You’ve picked your future alma mater and sent in your commitment to enroll. Decision made, deposit paid, now all that’s left to do is finish your senior year of high school without fading. We’re not talking about the standard bout of senior-itis, and we wouldn’t hold it against you for letting (a little) loose to celebrate your high school accomplishments and post-high school plans. But don’t go too wild, because on virtually every college acceptance letter there is some important fine print: The college reserves the right to revoke your admission. It’s hardly common for colleges to reverse their offers of admission. At most schools it affects less than about 1% or 2% of admitted students. But it does happen every year. “Because of the way the offer of admission often occurs halfway through the senior year, (admission) is contingent upon successfully completion of the senior year in a manner that’s consistent with how a student applied,” says Stephen Lee, associate vice president for enrollment management West Virginia University. In fall 2009, 22% of colleges said they’d revoked an admission offer, according to the National Association of College Admissions Counseling’s annual State of College Admissions report. The association hasn’t asked colleges about revoking admissions more recently, and most of the 20 colleges MONEY contacted about the practice declined to answer questions about it. Gonzaga University Dean of Admissions Julie McCulloh says she usually sends a warning letter to students whose grades drop a bit. She generally reverses about two admissions decisions a year for lowered grades when an applicant’s GPA falls significantly. One student last year, for example, maintained a 3.4 GPA throughout high school, and then earned four Ds and a C in his second semester of senior year. Another earned a mix of As, Bs, Cs, and Ds, but his overall GPA dropped in his senior year by almost a full point. Unsatisfactory final grades are the most common reason for revoking admission, according to past NACAC surveys. Disciplinary actions—which can include school-related issues, such as cheating, or legal issues, such as drug or alcohol offenses—come next, followed by submitting an application with false information. False applications usually involve students who have already taken college courses but apply as first-time students to cover up poor grades. Other times, it’s more innocent, and the student just didn’t consider the previous college experience to be relevant, says Lee of WVU. Regardless, it’s a red flag colleges that will follow up on. Public colleges are more likely than private ones to rescind an offer of admission due to final grades (84% of public colleges had done so, vs. 49% of private ones in 2009). A college’s selectivity made little difference in its likelihood of rescinding an application based on grades, but more selective colleges were more likely to do so because of disciplinary infractions. So what are your options if you think your acceptance status may be changed? Unfortunately not much—which is why it’s important to finish strongly in the first place. But you can ask if it’s possible to defer enrollment until the spring or following fall semester with an agreement to raise your GPA through courses at a local community college in the meantime. If there’s some extenuating circumstance that explains falling grades or unusual behavior, be up front with the college about it. Bear in mind, though, that any appeal is likely to be a long shot. Paul Seegert, admissions director at the University of Washington, says the university revokes 10 to 20 acceptances letters each year, mainly for grades, and even though students have the option to appeal the decision, that rarely results in a change.