When playing Road to Glory mode you will notice that you earn recruiting points after completing games. Each set of points that you earn will increase your prospect (stars) rating, and will also increase your chance for scholarships from big-time colleges. Earning 5 stars is not hard at all when playing on Freshman difficulty, as you will earn around 300 points and a star after each game.
You should be a 5 star prospect by the fifth game of your high school season if you're playing on freshman difficulty. You will also be able to earn the 'High School Champ' achievement if you play and win the high school championship game.
The achievement will unlock after signing to a college.