Yes, it is possible to drop a course after the beginning of the term, but there is a course withdrawal deadline to respect to avoid it being recorded as a failure on your transcript. This date is found in the school calendar for each semester.
Before proceeding, your child can get advice from their academic adviser to evaluate the impacts of such a decision on their school career (extending their education, summer courses, etc.), and by the same token, verify if alternatives are possible.
All courses dropped after the official deadline will receive a failed grade on the student’s transcript, which will be calculated in their R score, even if the courses are retaken and completed.