A future Princeton Tiger, Chmielewski spent a postgraduate year at Phillips Exeter following a standout career at Needham High School during which he was a two-time Bay State Conference All-Star. After earning 2018 Boston Globe All-Scholastic honors as a junior, he capped off his Needham career with a 5-3 record, 1.70 ERA and 71 strikeouts over 60 innings last spring.

The 6-foot-1, 190-pound lefty went 7-2 with a 1.40 ERA while helping Needham clinch the Division 1 state championship in Massachusetts as a junior. Chmielewski also played four years of hockey for the Rockets and continued his career in that sport at the prep level over the winter.