You will actually extend 24-months past your school's graduation date. Once you graduate and are awarded your new MOS, you will reenlist within 90 days for Option 1, Regular Army (aka, the needs of the Army) and get paid a bonus.
If you reenlist in Iraq (I assume you are there) and get paid that bonus, you cannot go into the BEAR program because you have to be within 24-months from your ETS to apply for the BEAR Program.