I had all my kids read How to Win Friends and Influence People their freshman years.
Recommended Millionaire Next Door later in high school but that one didn’t stick. They’ve heard me preach enough on that particular book anyway. Went with a Dave Ramsey book instead.
I think To Kill a Mockingbird is an outstanding choice.
For a bit of appreciation of U.S. history, I’d try to see if you can get The Killer Angels to take. For enjoyment and a bit of perspective on sports and competition, I’d try Friday Night Lights
and The Boys in the Boat.
If you can get your high school boys to read all those, I’ll be impressed.