Be patient: the schools are having a hard job deciding whom to accept and whom to reject and whom to wait list. (read here and here and this funny one)

Be careful about having your acceptance revoked. When admissions officers get together, they tell stories of students whose acceptances were revoked because the students either blew off the last semester of senior year, plagiarized OR required disciplinary action OR posted something really stupid to the admitted student FB group, etc. The fine print of your acceptance will list reasons the school can change that acceptance to a rejection. This doesn't happen often, but it does happen, every year. Don't let it happen to you! 

And consider these antidotes to anxiety.

If your IB scores matter to schools, you need to tell UAS which schools you want scores sent to.  Mr Koss told the Class of 2016 to use this form by 24 April 2016.

Consider how you will decide which school to attend if you are accepted by more than one school. If possible, talk to students at your schools. Would visiting again, with all you've learned since you visited before, make choosing easier? Plan out the first year courses you would take at each school: are you excited about taking these courses? Weigh the costs. Consider the benefits. Once you have several offers, start informing the schools that you know you won't attending so that others can have your place. A template for a letter is here.

If you're put on the wait list, let the college know they are your first choice. Send an email to the director of admissions expressing your continuing strong interest and updating with any new info that reflects well on you. Ask your counselor to contact them on your behalf. College want to admit students on the wait list who will accept the offer of admission rather that students who have already decided to go elsewhere. (Note: often there is little financial aid left to offer wait listed students.)

Statistics (2010) on being wait listed is here. Information is also at the end of this document.

If you're rejected know that this is not the end of the world. For candid advice on how to deal with rejection read this and this and this and this.

Do senior year grades matter? You bet! UAS sends seventh-semester grades as part of your application. Colleges expect you to show you are ready for college-level work. It is NOT AT ALL rare for a college to withdraw an offer of admission if grades drop significantly during senior year. Read about this happening here and here.