You’ve put in the hard work, earned good grades, participated in plenty of extracurriculars and written a killer essay.

And it paid off in the form of a letter of acceptance to a college you feel great about. So now it’s time to kick back, relax and enjoy what remains of senior year, right? Almost.

Though you should certainly celebrate your achievements, colleges reserve the right to revoke that acceptance right up until move-in day. “A myth that a lot of kids believe is that once they get accepted, they’re in,” says Liz Shapiro, a guidance counselor in Long Island, New York, and co-founder of Two Sisters College Consulting. “Actually, it is written in every acceptance letter that admission rests on the continued performance of the qualifications the student was accepted with.”

Revoking admission is certainly not an everyday occurrence, but it is something to keep in the back of your mind. From inappropriate social media posts to letting your grades seriously slide, here’s why colleges might say “No, thanks” after all.

Falling Grades

This is the most common reason a college might revoke — or think about revoking — an acceptance. If you were accepted as an A student and all of a sudden your GPA seriously drops, that is going to raise a red flag to colleges, which typically continue to monitor accepted students’ grades. Shapiro says not to panic if you get a B-, but beware of Ds or Fs. “These are good enough reasons for a college to say, ‘We’re not going to take you anymore.’”

Jason Patel, founder of college consulting practice Transizion, knows that senioritis can get the best of students post-acceptance. “We get it,” he says. “You’re on to the next four years of your life, and admissions tests and college applications are behind you. But it’s important to keep a B average in all of your classes.”

Social Media Gone Awry

These days, social media can have a big impact on your college applications regardless of what stage they’re in, a fact that ended up in the national spotlight when Harvard recently rescinded the applications of 10 students for posting inappropriate content in a private Facebook group.

Shapiro says that in her experience, teens tend to think that their social media activity — whether it’s on Snapchat or in a secret Facebook group — is private, but that just isn’t the case. Anyone can take a screenshot, and things can and do go viral in a heartbeat. So she advises her students not to post anything inappropriate, including sexual content, anything resembling bullying or harassment or even pictures with red cups (which can give the impression of underage drinking). “Recently, we’ve been talking a lot to students about promoting themselves on social media as opposed to doing these negative things,” she says. You can do this by posting about your accomplishments — say, sharing that big score in the game or a link to your stellar new piece in the student paper.

Patel takes a slightly different approach and advises teens to play it extra safe and stay away from social media entirely during this sensitive time. “We recommend all our students go ‘dark’ between the beginning of senior year and the summer before college,” he says. “In today’s online environment, any image or short message can be misconstrued.” If something negative goes viral, your admission offer could be in danger.

“Colleges want people who are good citizens to be part of their communities. The moral character is extremely important to them.”

Disciplinary Issues

If you think colleges only care about grades, think again. The way you act can be just as important. “Colleges want people who are good citizens to be part of their communities,” says Shapiro. “The moral character is extremely important to them.”

Chris Reeves, a high school counselor in Fort Mitchell, Kentucky, and board director for the National Association for College Admission Counseling, agrees. “Students need to understand that they are being accepted to schools as a whole person,” he says. “Their actions [of all kinds] matter.”

So be careful of letting too loose, especially if your behavior could result in disciplinary action from your school or, worse, an arrest. Colleges are wary of bringing those they identify as troublemakers who they fear will face additional disciplinary actions down the road into the fold.

Phony Information

Although it’s incredibly unusual, there are cases where students deceive their way into college — either by “innocently” boosting their application or flat-out lying. If a school finds out, that is immediate grounds for reversing its decision. “Every now and then, we run into parents who want to write the essay for their child,” says Patel. “This is not a good idea. Not only is it unethical and can lead to an admissions disaster, but it also teaches the student the wrong principles on how to succeed in college and life.”

In a recent case at the University of Rochester, a student’s admission was rescinded when the college learned that her entire application had been fabricated, from transcripts to letters of recommendation. That is an extreme example, but it serves as fair warning for anyone who thinks they can pull a fast one when it comes to college admissions.

Can I Appeal the Decision?

If you find yourself on shaky ground, don’t give up. Instead, course correct. When slipping grades are the issue, colleges will typically send a warning letter. Shapiro cites a former student who had one grade nosedive and received a message from Cornell, where he had been accepted, informing him that if he didn’t improve, his admission would be revoked. Armed with this information, he brought his grades back up and ended up attending.

Reeves, meanwhile, had a student who was accepted to an elite northeastern college and was told in June that a D grade in one class was grounds for rescinding his acceptance. He advised the student to explain what happened without making excuses. “You have to own responsibility and be honest,” Reeves says. This worked out, and the student was able to attend in the fall.

Experts agree that colleges tend to be less forgiving of behavioral mishaps. Not only do they want upstanding citizens at their school, but they also have a reputation to uphold and don’t necessarily feel comfortable taking a chance on someone who might jeopardize that.

In the end, colleges don’t want to rescind acceptances, but they do expect that future students will maintain the same standards that got them accepted in the first place.