It's good practice to record it
It's not a requirement for most schools, but you should still consider how best to record 'serious incidents' involving the use of force.
See the DfE's guidance on the use of reasonable force (see page 7).
Requirements in residential schools
In boarding schools, you must keep a record of the use of reasonable force (see appendix 2 of the national minimum standards).
In residential special schools, you must legibly record the use of reasonable force within 24 hours of the incident (see standard 12.6 of the national minimum standards for residential special schools).
How to record incidents
How to write the report
Make the record as soon as possible after the event, and within 24 hours, setting out a 'full picture' of what happened.
If more than 1 member of staff was involved, they should create individual reports rather than collaborate on a single report.