Dennis attended Montini Catholic High School for two seasons. For his junior year, he transferred to Oswego East High School and averaged 17.2 points and 4.9 assists per game.[1] As a senior, he averaged 23.2 points, 5.1 assists, 4.9 rebounds and 2.5 steals per game.[2] Dennis committed to play college basketball at Boise State, choosing the Broncos over 26 Division 1 offers.[1]
College career
As a freshman, Dennis averaged 4.1 points, 1.8 rebounds and 1.8 assists per game. He posted 8.6 points, 3.0 rebounds, and a team-best 2.9 assists per game as a sophomore. Dennis opted to transfer to Toledo after the season.[3] Dennis averaged 12.7 points, 4.0 assists and 5.6 rebounds per game as a junior.[2] On March 3, 2023, he scored a career-high 32 points to go with seven assists in a 87–81 win over Ball State.[4] As a senior, Dennis averaged 19.5 points, 4.3 rebounds and 5.8 assists per game, leading Toledo to a 27–8 record and Mid-American Conference regular-season championship. He was named MAC Player of the Year. Following the season he transferred to Baylor, choosing the Bears over Illinois, Michigan and Utah.[5]