IF they did all request the same room at the same time, then the school authorities would have a tougher decision to make, obviously.  A compromise would have to be worked out or process designed for how to deal with scarce resources.  

Reasonable accommodation is not a judgment made on hypothetical situations, but on real situations:  

"The acceptability of legislation or governmental action which could be characterized as state aid for religion or religious activities will have to be determined on a case by case basis."
~ R. v. Big M Drug Mart [1985, SCC]