New Install - Looking for user/group organization guidance

We're a rural school, 200 students. Grade 5-12 all have a device, as do teachers. K-4's have access to a iPad cart.
We just moved out of our UTM and into a XGS 2100. (4 - AX320 on the firewall, 4 - AP55 on Central)
Our WIFI setup was never quite ideal and now that I've got a new box, I'd like to set it up better.

We had our system set up whitelisting every device on by MAC address. No sign-in accounts on the UTM.

What I'd like to be able to do:
- See the network load at a goup/per-class basis at any time. (Teachers, iPads, Grades 5, 6, 7, 8, 9, 10, 11, 12)
- Schedule time based access per group
- Be able turn on/off YouTube access per group quickly/easily
- Filter policy/Application filter per group

I had thought to setup a WIFI for each of these groups, but not sure if that is an unnecessary number of SSID's all piling up on top of each other.
AND, after a more than one support call, could not get from a Central Managed AP via VLAN to the Firewall to see the internet.
If the classes can come into the firewall on fewer SSID's but still be managed as groups by some definition, that's fine.

What I don't want:
- I don't want to register my students as users on the firewall. I don't want the extra password management. And students will just share accouts/passwords to get around the system.
- I don't want to manage duplicate MAC address lists on Firewall/Central. If I have to use Central (and I do in order to use my AP55s), then what ever needs to be managed/defined on the Central side must not need to be duplicated in the Firewall. (I'm willing to move the firewall manged APs to Central if that simplifies matters. They are just there as that was the first internet access that worked when we set up.)

Support seems to be really good at answering specific questions if I know what I already want. They don't seem to be so good at explaining theory of the system's workings.

1. In the different possible layers of management in the firewall, how should I be defining my classrooms into groups so that I can mange them the way that I want?