What qualifications are needed for an electrician to test in a school?

The electrician must be competent and hold either the C&G 2391 or the newly brought out 2394-5 qualification. If he doesn't hold a inspection and testing qualification, I wouldn't class the electrician as competent myself. Also your electrician has been accessed in a domestic environment for electrical work and not commercial, for this you should be looking for an Approved Contractor with the appropriate testing qualifications as I'm sure the schools insurance company would not accept a testing report from a Domestic Installer and only of an Approved Contractor.

Just give NICEIC a call or go on their website where you can chat online. As far as I know he can't.

17th edition and 2391 testing and inspection with a membership to one of the following governing bodies NAPIT / NICEIC / Elecsa