If you are interested in being an athlete at a Division I or Division II school, you must be eligible according to the NCAA Rules.
Start here by Registering to the NCAA Clearinghouse. (Link to http://www.ncaa.org/student-athletes/future/eligibility-center)You must do this at the beginning of your junior year.
NCAA Guide for the College Bound Student (Link to http://www.ncaapublications.com/productdownloads/CBSA17.pdf)
DI Initial-Eligibility Quick Reference Sheet
DII Initial-Eligibility Quick Reference Sheet (Link to http://www.ncaa.org/sites/default/files/2017_DII_Requirments_Fact_Sheet_20170103.pdf)
Make sure you let your guidance counselor and/or your coach know if you have any questions about the NCAA Eligibility process.
This PowerPoint contains information regarding college athletic eligibility for NCAA D1, NCAA D2, NCAA D3, and NAIA.