Technically, no Junior can commit to any school at any level because the only binding commitment is the NLI which isn’t signed, at the very earliest, until Nov of senior year. However, many students give and get a verbal commitment from the coach that if the student is admitted, the student will attend and have a spot on the team. Some of these early commitments are much more of a sure thing because the student is likely to be admitted to a school with or without the coach’s tip/slot/support with admissions.
My daughter signed her NLI before she was officially admitted to her school.