Q: NEED HELP REMOVING ADS!!!!!

Start up in Recovery mode. In the OS X Utilities screen, select Get Help Online. A clean copy of Safari will launch. No plugins, such as Flash, will be available. While in Recovery, you'll have no access to your saved bookmarks or passwords, so make a note of those before you begin, if they're needed for the test.

Test. After testing, restart as usual and post the results.

A firmware password has been set. If you don't know the password, you'll have to take the machine to an authorized service provider to have it removed. You may be asked for proof of ownership.

The school's IT department will have to solve the problem.