You can leave the TI graphing calculator at home thanks to this web-based TI-83 and TI-84 emulator. As with pretty much all emulators, this depends on a ROM image from the actual hardware to work. But ...
Cellphones aren't allowed, or you got yours taken away, and don't even talk about Game Boys or PSPs on campus. Man, high school is such a bummer. Until they ported Wolfenstein to TI-83 and TI-84 ...