jiu jitsu is what i would recommend. Physical development at those ages have a correlated impact on intelligence later on. And martial arts teach emotional regulation which is also correlated with better grades in school.
24 karma · joined January 27, 2021
As a side note it is important to not use the system as just a dump of ideas and loose notes. Those are good as a starting point but I would recommend that you go through your loose notes and ideas twice every week. This is so that you can either make them permanent notes or just throw them away.
One last thing is that I have found that the combination of this + anki makes it really easy for me to commit stuff to memory and really speeds up my learning process by a huge margin. I wish I had discovered this way of reading and learning when I was in uni xD
To help out with your question this https://teachyourselfcs.com/ is a resource i have heard good things about.