My son is just a tad under 6 feet and 120 now.
He spent a lot time over the past couple months strength training. He went from squatting 45kg to 85kg and benching 30kg 60kg in just 3 months.
His goal for 10th grade is 165lbs and squatting 140kg and bench 120kg. He is just starting to hit puberty so once that kicks in that will help.
Good luck to your kid...