@JorisMeys When you say silly stuff, what do you mean? Like messing up the computer by typing random stuff in the terminal, or changing a lot of settings? Use Timeshift to roll back to a previous state (plus non-admin account). If it's parental controls of what they see and do on the internet, that's a whole different ball game. Your kid will soon be able to get around most anything if they want to. But some ideas are here: https://www.digitalzen.app/blog/how-to-set-up-safe-browsing-for-kids-linux/