This kind of discussion will end up being the typical (French) disdain between people learning engineering in the public schools v/s the ones learning in these "practical teaching" private schools and vice versa.

There are good engineers in both, both have different approach to teach which fit different people. Both do generally good in the private sector after they're done with it.

As usual the people graduating from public schools will say the private graduates don't have the theorical foundation, and the private graduates will say the public graduates don't have enough technical skills when they graduate. In reality the decent students will pick up the theory from the practical projects and vice-versa.

If that matters, I did Epitech, which is similar-ish to 42 and all the people that graduated with me have decent positions and are in high demand by the job market. Some of them in big name companies.

This kind of private schools are a good alternative for people who don't fit in the public education by letting them just do practical projects with some direction and let them pick up the theory from there. Some people are really good self taught hackers but would otherwise drop out in typical education, but they can shine in these schools. I've met many.