2009-10: Toninato skated in 31 games for Duluth East HS in Minnesota as a sophomore. He scored 8 goals with 11 assists and was plus-11. Duluth East defeated Elk River to capture the Section 7AA championship. After falling to Hill-Murray in their first state tournament game, the Greyhounds defeated Lakeville North and Roseau to win the consolation title.
2010-11: Toninato was the third-leading scorer for Duluth East as a junior and competed for Team North in the Upper Midwest Elite Hockey League in the fall. In 29 games he scored 28 goals with 33 assists as the Greyhounds captured the Section 7AA title and reached the Minnesota AA championship game – falling to Eden Prairie. In 24 games with Team North he scored 11 goals with 8 assists and had 12 penalty minutes.
2011-12: Toninato made his USHL debut, skating in four games with the Fargo Force, and was the second-leading scorer for Duluth East in his senior season, finishing with 73 points in 31 games. He scored 1 goal and was minus-one with 2 penalty minutes in his brief tenure with the Force. Toninato scored 33 goals with 40 assists as Duluth East again won the Section 7AA championship and Minnesota AA consolation title. In 24 games for Team North, including three playoff games, he scored 10 goals with 15 assists with 30 penalty minutes and his 25 points trailed only Duluth East teammate Kyle Olson among Team North scorers. Ranked 149th amongst North American skaters in Central Scouting's final rankings, Toninato was the first of four Minnesota high school players chosen in the 2012 NHL Draft when he was selected by Toronto in the fifth round (126th overall).