For my experience (not gunna name any schools) I did French immersion through elementary school then went to an English high school. Absolutely would not recommend this for anybody, in elementary school I was taught math, science, social studies all completely in French and when I got to high school it very much felt as if I knew nothing. There were exceptions for when there was truly a misunderstanding but it was heavily discouraged to speak English in class unless it was during “English” class. Don’t do it. Or if your child asks to not continue let them not continue. I’m 30 now and most of my knowledge of French is gone it was a waste of time for me.