I think you will find, from those on here who run similar courses that the bike needs to:
1) be clean and lubed (especially chain)
2) have tyres pumped up to a suitable pressure
3) the brakes work
4) Not be a danger to the rider or others.
Sounds obvious, but I have heard tales of children turning up on bikes that look like they have been dragged out of the local canal, expecting the instructor to fix them prior to the lesson starting. As most riding is done off road (school playground etc) then lights and reflectors (and bell)are not really needed, but a nice to have...