If you looking to replace dualingo, check with your local library, they may offer free access to different language learning apps. I was able to get Rosetta Stone for free using my library. And they also have access to Muzzy and Transparent language.
Excuse my ignorance, and not trying to offend just asking a question.
Why is it a bad thing to wait till kids are 18 before allowing them this care? Kids make rash decisions all the time, and something that seems difficult to reverse should be a decision when they are at a more mature age.
I feel like this is one of those discoveries thats like, well duh of course it would work that way