In more than 25 years of coaching from the CYO level on up, Kapper's teams won more than 1,000 times, Kapper coached both basketball and football at his alma mater, St. Mary's High School. He was an assistant on the 1961 football team that compiled a 9-0 record and won the state Class A championship. However, he is better remembered by area sports fans as a softball coach. Kapper's Firestone team won the industrial league championship nine out of his 11 years as coach. His 1978 Firestone team won the National Industrial Softball Championship. In 1982, Kapper's Major Open team became the first Akron softball team to win a state title. That same squad placed third in the nation, and the next year, the team finished eighth.