I disagree, do not let them use internet as they wish. The age of 12 is so vulnerable for porn addiction, video game addiction, gambling gacha addiction, meme consooming addiction and all the psychological damage that slot machine style colours and visuals can do permanently to a kid’s brain early on. The kid struggles until they are 30, due to this.
Edit: let me just say, hand them over a book called “Irresistible” by Adam Alter. It is not difficult to understand, easy to read.