So wait , you want a good language arts/maths based multiplayer game to take to school? Is that right?
From what I understand he wants to sneak something other than that into his School.
I go to Edgewater High and something we all find fun is Minecraft. I'm assuming you want something where you can open a LAN server and quickly pick up and play games. Counterstrike 1 is good, Tribes 1 (if you can find it), Halo Custom Edition, and maybe if you can find it the cracked LAN version of Torchlight 2. Glad I could help!
Sources: I was looking for the same thing for a while.
Download the Halo PC demo. You can play through the Silent Cartographer level, and play online multi on the Blood Gulch map.
I'm surprised nobody has suggested that maybe you should just concentrate on school while at school...
This is why i like forum
Get Xonotic, just download the .zip from their website and copy it to every computer in the school, thats what i did...