Seems a very weird method of operation from the flying school, all the schools/FBOs I have used have always asked you refill to tabs on your return unless SPECIFICALLY REQUESTED by the following hirer not to!
I always refill to tabs (unless W&B prevents), before taking an aircraft out and will sometimes fillup at a midpoint enroute even if it doesnt require it.
You can never have too much fuel...unless you are on fire!