Yeah I stopped before high school though. For me it was biking everywhere that put my legs ahead for a bit. I think I might need to start training legs though as I can't really deadlift now due to a lower back injury and will need legs to compensate a bit for it, might be a muscle imbalance contributing to it (pain if I try deadlift for reps even on lower weights)
Get a deck of cards. Pull one card at a time and whichever card you pull do that many push-ups. Face cards are 10. Ace can be 1 or 11 depending on you (makes a big difference). Try getting through the full deck and if you can't then lower face cards to 5 or whatever fits you.