The short answer is yes! Colleges will ask us to let them know we plan to attend by asking us to accept an offer of admission and pay an enrollment deposit to secure our seat. But what about the colleges you applied to but don't plan on attending? Most students apply to anywhere from 5-14 colleges. Should you bother to let the college you are not attending know of your decision? Yes, you should! Here's why:
Colleges have a certain number of seats they can fill. They admit more students than there are seats available because they know a portion of those students will attend another school. However, there are also a bunch of students that really want to go to that college and were placed on a waitlist so they are waiting to see if you accept the offer. Letting the colleges know you don't plan to attend opens up the seat they are reserving for you.
Someone took the time to read your application. You should extend the courtesy they gave you by reading your application and let them know they are no longer a choice for you.
So, please, for the colleges you don't plan to attend, send an email to the admissions representative thanking them for taking the time to review your application and respectfully decline their offer of admission.