You're not required to have visitors sign in and out
It's up to you to decide whether this is appropriate. This also applies to parents and other visitors who attend events such as sports days.
However, it may be difficult for you to find a practical alternative that enables you to meet your health and safety obligations to visitors.
Carry out a risk assessment before inviting in a large group of parents. Make sure adequate arrangements are in place to enable your school to account for all staff, pupils and visitors in the event of an emergency evacuation.
The DfE gave us this advice.
Visitors may be particularly at risk in the event of a fire because they are less familiar with the premises. You should include arrangements for them (and anyone else who you’ve identified as at risk) in your emergency and