You have to activate the Captive Portal in Routed Mode on the interface connected to the wireless access point (ETH00 in your case).
You must assign to ETH00 an IP of the subnet 192.xxx.x.0 (this IP is the default gateway and dns for the student clients). After that, enable dhe dhcp server for the subnet 192.xxx.x.x and define an IP range of dynamic addresses for the clients. To the ETH01 you must assign an IP of the school’s network (10.x.x.x) and do not forget to assign to ZeroShell the default gateway for the net 10.x.x.x and put the ETH01 in the NAT list.
Before to activate the Captive Portal you should test if the student clients reach the external network.
In any case, for more details, you could read the Cristian Colombini’s guide
available at the URL http://digilander.libero.it/smasherdevourer/schede/linux/zeroshellEN.pdf