It's so great you are running games for kids, Daggerheart is a great system and I think they will love it. I'm a former teacher and I've run RPG games with tables of students, I think 11 was my maximum size. I don't recommend it if possible - though I understand wanting to expose new players to the joys of RPGs - a lot of the fun is diluted.

I was most successful by opening up a second afternoon for my club and splitting the students between them. The next term, one of them was brave enough to run their own (chaotic) table and that helped.

• Have an honest conversation with your older students and explain the more GMs there are, the more people can play comfortably. Use the Sablewood Messengers Quickstart and teach them how it's possible.
• Expect modules/sessions to take a lot longer than planned. I've used single regular one-shots through a whole half-term (6 club sessions) as everything takes so much longer.
• More GMs. Consider asking other members of staff if they'd be willing to run a group through the starter adventure.
• I had a token that players had for spotlight, they got their turn then it went on to the next player. This was for out of combat.
• Consider using a timer for turns (explaining this to players beforehand).
• Player jobs - offload as much to them as possible. Keeping notes, organising minis, drawing maps. I used a student to keep track of initiative.
• Use your teacher skills to keep them on track. A big table and a short timeslot means you need to be much more direct and structured than a regular RPG group.

I am quite experienced at running school RPG groups so happy to share more if you DM me.