 Cowels attended Hopkins High School in Minnetonka, Minnesota where he led his team to 128 wins with only six losses while winning two state championships in 2006 and 2009, and earning All-State honors twice and all-conference three times.As a sophomore in 2006–07, he averaged 11 points and six rebounds per game as Hopkins made it to the section championship.As a junior in 2007–08, he averaged 17 points and seven rebounds per game in leading Hopkins 27–2 record.