Playing at the under-16 level for the Halton Hurricanes of the South-Central Triple A Hockey League in 2022–23, Schaefer recorded 12 goals and 32 points in 25 games, earning player of the year honours.
[8] In January 2025, not long after sustaining a broken collarbone at the 2025 World Junior Championships, he was named the top North American skater on NHL Central Scouting's midterm rankings.
[9] Representing Ontario at the 2023 Canada Winter Games, Schaefer, as the team's captain, scored an game-winning goal in overtime of the finals to secure a 3–2 victory over Saskatchewan and a gold medal.
[13] He opened the tournament with two goals in a 10–0 blowout victory against Switzerland,[5] adding four assists over the rest of the event to finish with six points.
[14] After scoring a goal and assist in the first game of the 2025 World Junior Championships, Schaefer suffered a broken collarbone in the following match, a 3–2 upset loss to Latvia.