NASUWT believes that the number of learners in class impacts upon the workload and wellbeing of the teacher.

Excessive workload has a huge impact on teacher health, safety and wellbeing undermines teachers’ ability to teach effectively.

Whilst the job of teaching has always been demanding, government and administrations have a responsibility to intervene and schools have a duty to take action to tackle any excessive workload and any threats to the health, safety and welfare of their staff.

This briefing updates members on the NASUWT position on class sizes, the present position in Wales and across the UK.

If members are concerned about their class sizes this briefing also suggests a way of dealing with class size through the use of risk assessments.

NASUWT class size checklist

• You cannot be expected to teach effectively if your class size is excessive and unmanageable.

• Excessive class sizes impact adversely on the physical and mental health of a teacher and where a school or college fails to take appropriate steps to tackle excessive class sizes/workload pressures, it may be held liable.

• Schools and teachers should conduct risk assessments on any activity to determine whether the class size is too large for that activity.

• This assessment will include different factors relating to health and safety and also to excessive workload and teacher stress.

Educational recommendations

These general educational recommendations below on class sizes set out the following limits, which, if exceeded, raise the possibility of an impact on teacher wellbeing and stress:

Recommended limit	Class type
26 pupils	in the case of early years foundation stage classes with one teacher and a support staff member with minimum NVQ level 3 qualification
27 pupils	in the case of KS1 classes
24 pupils	in the case of mixed-age classes
20 pupils	in the case of practical classes
15 pupils	in the case of classes of pupils needing particular small group or individual attention
30 pupils	in other cases

What does it look like in Wales?

A recent NASUWT Cymru Survey (October 2024) demonstrated class sizes of:

• foundation: 26-30 pupils;

• KS2: 26-35;

• KS3: 26-35;

• KS4: 16-35;

• KS5: 10-15;

• ALN provision: 10-15.

This briefing references other risk factors to be included in a risk assessment such as type of activity, mixed ages, room layout, subjects that need teaching assistant support as well as teacher input.

When conducting a risk assessment on class sizes, the factor of stress impact on teacher wellbeing should also be considered, including the impact of increased workload from marking a large number of pupils’ workbooks.

Time for a Limit

The key to determining whether the size of a class is too large is the risk assessment process.

Any activity should be risk assessed and this should include consideration of a number of factors, many of which are interlinked:

1. The physical environment, including the size of the classroom, the layout of the room, whether furniture is fixed or moveable, the ease of movement around the room, any mobility needs for pupils or staff, the number of exits, the location of the room in relation to others, i.e. is it isolated, can help be summoned quickly if required?

2. The activity to be performed - are there any inherent risks, is there any potentially dangerous equipment to be used?

3. The dynamics of the class in question - do any pupils have behavioural issues, are there additional adults in the room, what is the knowledge and experience level of the pupils/students?

4. Any existing/generic risk assessments - do these indicate any precautions that should be undertaken or any minimum ages for the activity, etc?

5. Advice from subject associations, such as DATA, CLEAPSS, SSERC etc. These organisations publish advice and guidance for specific subjects and activities. There are specific examples of these in the Further class and subject specific guidance below which will help you create your risk assessment.

It may well be that a certain activity in a certain room is deemed safe, whilst it can be deemed unsafe with the same class in a different room. For example, using Bunsen burners with 30 pupils in a large classroom with plenty of space may be safe, but trying to do it in a very small, overcrowded room would clearly be unsafe.

Likewise, doing this activity with 30 non-ALN pupils may be safe, but undertaking it with ten pupils with behavioural issues may be unsafe without additional precautions, which could include additional staff. There is no one-size-fits-all approach.

It could also be that, irrespective of the activity, the class size is too large due to factors such as the difficulty evacuating the room in an emergency (the fire risk assessment may need to be consulted) or a lack of sufficient ventilation.

It cannot be stressed highly enough that it is the classroom teacher who is responsible for risk assessing activities in their classroom, whether that be quiet reading or use of concentrated sulphuric acid.

Teachers risk assess constantly and often without realising it. Risk assessments do not have to be written down. However, if there is a specific hazard, such as a practical activity, it is recommended to do so. If there is an accident, the risk assessment will be requested. If in doubt, write it out.

Where there are specific risks and/or a risk assessment is required, training on how to carry out a risk assessment should be provided.

The Health and Safety Executive provides a Health and safety checklist for classrooms which can be useful in the risk assessment process.

If, in the teacher’s opinion, having carried out the risk assessment, the risks are too great, then the activity should not take place without additional precautions to ensure the health and safety of all concerned.

Remember: it is the teacher’s responsibility to ensure the activities in their classroom are safe. If this is not the case, do not proceed with the activity.

If the activity is required for curriculum reasons, this should be discussed with the line manager, head of department, etc. to identify further measures that can be taken, but do not proceed if you are unhappy or concerned about the risks.

If necessary, and particularly if you are being pressurised into carrying out an activity that you believe is unsafe, contact the NASUWT for advice.

NASUWT has also published UK-wide advice on Class Sizes setting out the evidence underpinning the educational case for smaller class sizes.

If you would like to access guidance to complete a risk assessment, please contact the Wales/Cymru National Office on 029 2054 6080.

Together, let’s do something about excessive or hazardous class sizes/activities.

As a member of NASUWT, you are not alone in dealing with the problem.

Working together, members are encouraged to take action to insist on working practices that are manageable and safe and to make sure they have the time to do the job.

In many individual settings, NASUWT members are benefiting by working together with their school/college to tackle problems.

It is important that your concerns are taken seriously and addressed by:

• arranging to meet with other members in the school to talk about the issue in your school/college;

• raising the issue with your NASUWT School/College Representative or meeting with your NASUWT Local Association;

• meeting with the headteacher or principal to discuss the problem and to agree solutions;

• with the help of your NASUWT National Executive Member, agreeing on appropriate action that can be taken to protect members at your school, including collective action to insist that your school/college takes effective action to stop any unsafe class sizes or activities.

Support and advice are available from NASUWT for members. You can seek support and advice from NASUWT directly if you are concerned that your school/college is not taking appropriate action to support and protect you and other members.

NASUWT will continue to press all governments and administrations to take action to ensure safe working conditions for all members.

The Valued Worker Scheme, endorsed by NASUWT and other unions, aims to promote good employment practice in schools and colleges and recognises those employers that are taking effective action to tackle excessive workload and to assure the health, safety and wellbeing of teachers.

Further class and subject-specific guidance

DfE guidance

In general, DfE advice has tended to focus on the relationship between pupil numbers and available teaching space. Over the years, this guidance has envisaged, for example, a figure of 20 pupils in an average sized design and technology classroom (around 100m²).

Primary schools

In primary and middle schools, the ‘standard’ classroom size for a class of 30 pupils is around 70m² (see Building Bulletin 99: Briefing Framework for Primary School Projects).

Such space limitations automatically place restrictions on the amount of ‘free’ space available in the classroom. This impacts on the types of work attempted and the ability of teachers and classroom assistants to engage and supervise safely and effectively.

For more complex design and technology, science or art projects, many schools make use of shared specialist practical areas which can be accessed as required by all classes on a rota basis. It is less likely, however, that such space will be available in older school buildings.

Secondary schools

For secondary schools, the most current guidance document relating to class sizes in practical lessons is Building Bulletin 98: Briefing Framework for Secondary School Projects.

This gives area guidelines for different subjects depending on the activities taking place in them. These are summarised in the table below.

Recommended area (m²) according to group size

Space type	For 20	For 25	For 30
Standard classroom	43	51	60
Science laboratory KS3/4	-	77	90
Sixth-form science laboratory	90	105	-
General art room KS3/4	-	77	90
Large art room (textiles or 3D)	-	90	105
Sixth-form art room	77	90	-
Textiles room	85	-	-
Graphic products	85	-	-
Electronics and control systems	90	-	-
Resistant materials	112	-	-
Resistant materials/engineering	116	-	-
Food room	101	-	-
Music classroom	-	57	67
Drama studio/music recital room	-	77	90

It is advised in this guidance that in design and technology group sizes will not exceed 20 students.

Regrettably, the government’s funding model for schools announced in 2012 recommends reducing classroom sizes. The plans involve reducing overall gross area by an average of 20% in special schools, 15% in secondary schools and five per cent in primary schools. However, these cuts only apply to new-build schools.

The Design and Technology Association (DATA) and British Standard 4163

DATA advises that at KS3, class sizes of 20 should normally be manageable, reducing to 18 at KS4 and 16 for post-16 classes. It furthermore suggests that determination of class size will ‘require the exercising of professional judgement by the head teacher and the subject leader.

Another authoritative source of guidance is British Standard 4163:2007 on safety in design and technology in schools. BS 4163:2007 states that ‘in England and Wales the recommended maximum number of students in any one work area is 20 students with one competent, qualified teacher’. (Para 3.1.)

The employer may choose to control the risk by another means, but it must control the risk. For example, the employer may decide to employ two competent and qualified teachers for one group in an area if the number exceeds 20.

Moreover, BS 4163:2007 states that a risk assessment should be carried out to determine the appropriate number of students and that this should be carried out in accordance with the publication Risk Assessment in Secondary School Design and Technology Teaching Environments, which is available from DATA or by telephoning 01789 470007.

‘Suitable and sufficient’ risk assessments are an explicit requirement of ‘The Management of Health and Safety at Work Regulations’.

Design and technology department risk assessments should facilitate both a safe place of work and safe systems of work. A competent person should carry out the risk assessment.

Science laboratories

As far as science classrooms are concerned, the now out-of-print DfE publication Safety in Science Laboratories 1996 states, ‘There is no statutory limitation on class size in any subject in schools in England and Wales. Teachers who are concerned that risks in practical work are increased to an unacceptable level because of the class size should report their concerns to the head of their science department and, if necessary, their head teacher. It may be possible to adopt alternative methods for particular pieces of work. However, if risks cannot be made acceptable, the activity must cease until it can be resumed safely.’ (Para 7.6 page 25.)

Building Bulletin 80, Science Accommodation in Secondary Schools, which is an archived publication and may not reflect current government policy or guidance, recommends a space range of 83 to 99m² for a group of 30 KS3/4 pupils, adding that ‘the range of activities being undertaken, the level of storage kept in the laboratory, the number of pupils with special needs, and the type of furniture system used can all affect area requirements’.

It should also be borne in mind that some local authorities will have established their own rules about maximum class sizes for science lessons.

Physical education

Again, no statutory limit is placed on class sizes in PE lessons. In determining staff/pupil ratios, therefore, it is necessary to rely on health and safety legislation and in particular the risk assessment process (see below[link]).

In particular, when determining the size of teaching groups in PE, account should be taken of:

• the nature of the activity;

• the location of the activity, e.g. indoor/outdoor;

• the age, experience, maturity, competence and behavioural/emotional characteristics of the pupils.

The school or local authority has a responsibility to carry out ‘suitable and sufficient’ risk assessments in all curriculum areas, including PE. Where there is a gap in such provision, the school/local authority is failing to comply with the law.

If the teacher disagrees with the conclusion of the risk assessment, and the provision for safety in class size, this should be escalated within the school for further review.

Other practical subjects

The above table gives useful indications of minimum standards across a range of other practical subjects including music, drama and art

A live risk assessment is crucial in assessing the specific nature of educational activities being undertaken, variability in pupil abilities, experience of staff, and age and design of buildings can all add to the risk assessment.

Pupils with additional learning needs - special schools and mainstream

Many pupils with ALN are at particular risk in practical activities and this is an important factor when considering group size.

It is probable that those pupils categorised as having ALN will need extra support. This will vary and the ALN co-ordinator in school will be able to advise further on this.

A risk assessment should take into account the mix of a range of abilities. A high number of pupils with ALN would require a smaller class size.

Building Bulletin 102: Designing for Disabled Children and Children with Special Educational Needs gives details of ‘typical’ pupil-to-staff ratios for practical work in primary and secondary special schools.

Building Bulletin 102 can be found on the DfE website.

General health and safety legislation

The Health and Safety at Work etc. Act 1974 places a general duty on the employer to ensure, so far as is reasonably practicable, the health, safety and welfare of its staff and pupils.

This means that it is the employer’s responsibility to put such arrangements in place with regard to class size in practical lessons to ensure that the risk of harm be properly controlled, a process which should be done by means of a suitable risk assessment, as required by the Management of Health and Safety Regulations 1999.

A thorough risk assessment on class size in practical subjects will determine the available space, equipment, furniture, activities and pupil characteristics and from thence the appropriate staffing levels and maximum pupil numbers.

A risk assessment will entail a careful examination of hazards likely to exist, an assessment of whether the particular hazards are likely to harm anyone and what precautions need to be taken.

Inexperienced teachers need time and support in order to develop the demanding skills required for the successful delivery of practical lessons. A suitable ‘cap’ should be placed on pupil numbers in practical classes taken by less experienced teachers.

Employers have specific legal duties to carry out risk assessments for all areas of workplace health and safety and to appoint a ‘competent’ person or persons to carry them out.

If the rooms are so designed that, as the teacher circulates within the work area, a clear view cannot be obtained of all working situations, it will be necessary to reduce the size of classes.

HSE checklists

• Health and Safety Checklist for Classrooms (English) (pdf)

• Health and Safety Checklist for Classrooms (Welsh) (pdf)