Suggestions for large school group for dinner in Paris?

You can't reserve but if you go early i.e. line up at about 6:30 for 7 pm dinner you can get huge choice of classic French foods for well under 20 a head including wine if you like at the Bouillon Pigalle.

We had a very nice 3 course meal with friends here: the link lets you examine the menu in English and see the variety and the prices.
http://www.bouillonpigalle.com
This place is huge and could accommodate a large group; if you wait until later, it will be crowded and a bigger problem. We went early and at 6:30 or so the place was nearly empty and could have put 40 people more or less together. The room itself is not special. I had the lamb stew which was lovely and the most expensive main course at about 12.50. My husband had a lentil and sausage dish for about 8.50 and our friend the Boeuf Bourguignon. We had a liter of rose for some ridiculous price -- I think it was 8 Euro or so. There are lots of soft drink options as well of course as the always free tap water which helps keep the cost down in France.

There are other Bouillon in Paris similar in menu. One with the most charm but also more crowded is:
https://www.bouillon-chartier.com/grands-boulevards/
We have eaten in the older one and it is also huge and cheap and I would assume that going early you would be able to be accommodated. It is beautiful and the kids will feel like they are in Paris with the waiters in black with white aprons and the bill toted up on the table cloth (l'Addition).

I have not eaten at the newer one in Montparnasse, but it looks beautiful from the pictures.

This is a very tough request between the number in your group and the budget and the location. That being said and assuming mediocre food is okay, take a look at Chartier Montparnasse.

Cheap food and a huge menu guarantee mediocre food but one of the advantages of the bouillon which were originally created to provide cheap filling food to workers, is that they offer the kind of variety that works well with teenage picky eating and appetites. They will all be able to find something. In our experience of both Pigalle and Chartier bouillons, the food was fine -- and at Chartier the room and ambience was wonderful.

Student groups often eat at Flam's, which serves what's basically an Alsatian-style pizza. They do affordable all-you-can-eat options and tend to work well with picky eaters. There are several locations in Paris, and you can do group reservations in advance - this page is aimed at tour operators but is in English. The French reservation system might honestly be pretty easy even if you don't speak it, just be careful to do date / month / year when indicating the date you want.

Pretty much they just keep bringing around the flammekueche / tarte flambée and everyone digs in until finished. It's not the most amazing food, but it avoids a lot of the difficulty of getting everyone to pick and most teens will find something they like there.

I’m thinking about staying in the vicinity of Saint Germain. Maybe a Hippopotamus could work out. There is one on Rue Lagrange in the 5th. I’ve never been but it should be in budget. There are a couple of other Hippopotamus locations in the 15th and the 14th that might be convenient to Saint Germain.

Three things come to mind as we’ve had experience on several trips booking group meals for 48 college students and leaders.

What dates are you looking for? We just ran into the issue of some of the Bouillon restaurants being closed in August for a week or two.

How old are your students and do you have a particular theme or course of study in Paris? We were studying art and history and managed to find some restaurants that fit the bill for our purposes.

Have you contacted the hotel where you are staying with a request for a nearby meal, date, menu options and budget? We often did this and they found neighborhood restaurants that would open a bit early for our group. This was my least favorite way of arranging meals because they were often very uninspiring. But sometimes we just needed to all eat together before an evening performance for example.

Check out Ristorante del Arte on Blvd St Germaine. It serves pizza, pasta, salads. They have a large upstairs area that could accommodate your group size. We ate lunch there in November and I want to say the pastas were about 9-12€. I think the menu is the same for dinner, and they have a daily menu option (entree + desert + drink) but I don’t recall the price. Service was fast and our server wasn’t super friendly, but that’s kinda the norm.

Sodas as so pricy (3-4€), but we were able to get tap water at all restaurants for free. Ask for un carafe d’eau. Pronounced “caraf dough”.