2010-11: Karson Kuhlman skated for Cloquet-Esko-Carlton in northern Minnesota and was the team's second-leading scorer as a ninth grader. In 27 games he scored 17 goals with 35 assists — including a five-point game (3 goals, 2 assists) in a 7-5 win over Hermantown — and had 8 penalty minutes. The Lumbejacks advanced to the Section 7AA semifinals with a 2-1 win over Andover in which Kuhlman had a goal and an assist before losing to Grand Rapids, 5-1. Kuhlman was selected by Dubuque in the fourth round (48th overall) of the 2011 USHL Futures Draft.
2011-12: Kuhlman made his USHL debut with Dubuque in March following his sophomore season at Cloquet-Esko-Carlton and played for Team North in the Upper Midwest High School Elite league in the fall. He had 4 assists and was +3 in five games for the Fighting Saints. In 26 high school games he scored 27 goals with 28 assists. The Lumberjacks finished 17-9 after a loss to Elk River in the Section 7AA quarterfinals. In 24 games for Team North prior to the high school season Kuhlman scored 5 goals with 11 assists and 4 penalty minutes. He attended USA Hockey's Select 17 Festival and was selected to play in the 2012 Ivan Hlinka Memorial Tournament.
2012-13: Kuhlman represented the USA in the 2012 Ivan Hlinka Memorial Tournament in August and in September committed to playing college hockey at Minnesota-Duluth in 2014-15. He played two regular season games with the USA NTDP U18 team and played in 27 USHL games — including 11 playoff games with league champion Dubuque — following his junior season at Cloquet-Esko-Carlton. Kuhlman had 1 assist and was -3 in four games at the Ivan Hlinka tournament and was scoreless with 2 penalty minutes with the NTDP U18 squad. He scored 1 goal with 8 assists and was +8 in 16 regular season games with Dubuque, which finished first in the Eastern Conference and was 9-2 in the USHL playoffs; sweeping Fargo in the Clark Cup finals. Kuhlman scored 4 goals with 2 assists and was +3 with 2 penalty minutes in 11 playoff games. He was Cloquet-Esko-Carlton's third-leading scorer, finishing with 27 goals and 24 assists with 6 penalty minutes in 27 games. He scored 2 goals with 2 assists in a 6-2 win over Forest Lake in the Section 7AA quarterfinals before the Lumberjacks were shutout by Duluth East, 3-0, in the semifinals.
2013-14: Kuhlman passed on his senior season of high school hockey to spend the entire season in the USHL and played for the USA in the 2013 World Junior A Challenge tournament in Canada. Kuhlman, an assistant captain, led Dubuque with 25 goals and had 19 assists, finishing +16 with 12 penalty minutes in 56 regular season games. Dubuque finished third in the Eastern Conference and defeated Cedar Rapids in the playoff quarterfinals before being swept by Indiana in the semifinals. Kuhlman scored 1 goal with 2 assists and was +3 with 5 penalty minutes in seven playoff games. In his second year of draft eligibility he was ranked 94th amongst North American skaters in Central Scouting's final rankings.