Ryan Prehn graduated from Taylorville High School in 1998. He lettered two years each in track and on the basketball team, but Prehn excelled on the football field where he earned three varsity letters and led the Tornadoes to an 8-2 record , were Central State Eight Conference Co-Champions and were selected play in the  IHSA State Playoffs his senior year.  Prehn also established many quarterback records during his senior campaign.  

As starting quarterback for the Tornadoes his junior year, Ryan passed for 1313 yards on 89 completions and 197 attempts. He was selected as an Honorable Mention member of the Central State 8 All-Conference team.

In 1997 Prehn established himself the premiere quarterback in the Central State 8.  He completed 118 passes for 2001 yards, a school and Central State 8 record and also led the CS8 in passing touchdowns with 20.  He set school records in total career yards passing with 3314, total career yards total offense with 3240 and career touchdowns with 33.  The Tornadoes finished the 1997 season 8-2 and advanced to the IHSA playoffs, losing in the first round to Normal Community 17-13.

Following the season, Prehn was selected All- CS8 Conference First Team Quarterback and All-Academic Conference .  Prehn was selected  All-State Honorable Mention and USA Today awarded him as an All- American Honorable Mention.

Following graduation, Prehn attended Illinois Wesleyan University where he also played on the Titan football team for two years.