And if you think Wharton is jumping up and down because a kid at a prep school was in the “investment club” (absent anything else compelling about the student) I have a bridge to sell you.
OP- the BEST business training for a HS kid is to work at an actual business. Or if the kid is too young in your state, start their own babysitting, lawnmowing, cleaning garages for elderly neighbors, “sports camp” for 6 year olds in the summer in the backyard, etc. This is the kind of business relevant for a HS kid. Kid has their entire life to learn about portfolio management and how to trade commodities.