It is unreasonable to ask a teacher to act as additional unpaid security for Sainsbury's. They have little authority outside of school.
Criminal behaviour is for the police to deal with - it seems pretty simple to me.

As for IDing the children, Sainsbury's will have tapes of the incidents and FHS have a duty to cooperate in putting names to the faces as part of any investigation, but for me their responsibility goes no further.

But what do I know - the Safer Schools’ Officer hopefully comes up with some new ideas that are acceptable to the manager.