The first day of school may still be a few weeks away, but football and volleyball practices have already started. Twenty years ago—when Denver Public Schools’ middle schools didn’t have athletic programs—kids would still be staving off end-of-summer boredom at home. The Denver Nuggets noticed the gap in sports programs and offered $360,000 to get the ball rolling (pun intended): In 1997, DPS Prep League, an after-school sports program for middle schools, launched with 600 kids participating in seven sports.

Today, more than 6,500 students compete in 17 sports thanks to $265,000 of help annually from Colorado’s pro sports teams. It’s proved successful at warming up athletes for high school teams: Since Prep League’s initiation, Denver schools have won nine state basketball titles, progressed from having the worst football league in the state to sending a team to the 4A State Championships in 2012, and earned the district’s first volleyball state tournament bid in 26 years this past fall—all while the athletes have maintained an average 3.19 GPA.