Red Robin

Pizza

Chipotle goes over well.

Chipotle catering, you can order either premade burritos or go with the ingredients individually.
Panera catering for sandwiches

You could make big trays of baked ziti which is easy and cheap, use aluminum trays from the grocery store. Or frozen lasagnas

So you'll need so something easy to eat (no utensils needed, a food that doesn't need to be heated, etc, right?).
Are you on a budget?

I mean you can't go wrong with pizza or CFA nugget tray for HS teens. Add a fruit tray with it.

Is this food for after a sporting event or like a post theater production celebration?

I'm not a cook, so likely looking to order pick-up or delivery for 40 kids to eat at school. What are your tips for the most cost-effective approach?

I'm also not a Costco member or anything similar, so that's not an option. TIA!