If you bridge the interfaces then you will only have one IP on the box for the remote management. All the traffic will flow through the box transparently. So your client PCs will have gateway IP address the IP of the gateway ZS.
You cannot limit each student independently unless you create one class map for everyone. They will share the bandwidth you allow for them.
Bridge is a bit faster than routing, but this is not something you’ll ever notice. Also take my advise and enable QoS only on the outgoing interface towards the internet.