This is a common problem. The best thing would be to let your employer know about the situation ASAP and also propose a solution.

Here is one solution:

Join a school and work through school (May to September 2008). Ask your company to sign an employment contract with the school. Even though this contract is not a big deal, it is your job to convince your company about it. Since this period falls during the summer, you’ll be able to work full time (if in school’s payroll). The only period you won’t be able to work full time is the beginning of fall semester till the end of September (2 to 3 weeks or a month at most). Hope this helps.