The only way this can actuaally be useful (like many people mentioned) is teaching about all/most of them from a neutral point of view without trying to force it on kids. Believe in a god or not religion is part of humanity so it should be talked about.
Don't know in other countries but I studied in a catholic school and what they taught was too biased to be taken serious, even more for me that I was an atheist. Definitely not the right aproach if you want to make it a proper subject imo