I don't believe that we have to choose between the two. Instead, we should ask ourselves how we could improve both programs.
If we concentrate only on immersion programs, it would be very difficult for all locations to offer them. We must seek to improve both programs. That way, it will create what you wish to see in the end; you will have students who, once they leave high school, after having followed the core program, or the immersion program, will have a level of French that is acceptable.
According to the results of our evaluation, at the end of the 12th grade, most students in immersion programs are able to meet the challenge of obtaining a B2 level. I don't know if you know the levels.