clearing house

You are asking about different issues here...

1. Getting into college has to do with GPA & required course work, SAT scores, etc. See the admissions dept. of the univ.

2. Playing sports in college means that in addition to the standard college acceptance, you must meet NCAA qualifiers academically to be eligible. See http://www.ncaa.org/ eligibility

Yes, if you do not meet the standards of the school,(academically or athletically) a school may withdraw an offer.
Pull out the green tab on the left. See recruiting tab...Here you'll find all the information you need.

If grades are an issue, pull out all the stops to get the help you need...Tutors, SAT prep, study groups, extra credit work...whatever!

Colleges will help athletes, but you still have do the work necessary to be eligible & stay that way!
Good luck, do your best!

kbs - Yes, if you aren't "cleared" by the clearinghouse, an NCAA school cannot give you a sholarship.

However, if you've signed with a NAIA or JUCO, the only academic standards/acceptance you have to meet is the schools.