Schools vary a lot. Some schools are really good, but a lot of them are bad. Schools are typically held back by those who don't care and so disrupt the class. (this isn't always bad, for kids learning how to deal with other kids is itself an important lesson - home school kids tend to do well on tests with much less time spent in study, but they always show a lack of meeting diverse people in my experience)
I learned French and my experience from best to worst ways to learn were:
1. 1-1 lessons with language teacher (by far the most effective way to learn)
2. audio lessons (Michel Thomas Method)
3. Visiting France a lot, interacting with French people (my wife is french) (and yes, for me this was less impactful than listening to audio lessons)
4. Duolingo (did a year of doing it daily, did almost nothing for me except a bit of vocab)
5. School (3 years of French in school was about equivalent to listening to 5 hours of Michel Thomas audio lessons)