The first picture looks like he could have some juice in his system. No way to know for sure from just the pics. I knew kids who did juice as early as 16 in school, so it is not beyond belief.
The first picture shows alot of definition and just based on my personal experiences and the people I have known, I would say he "could be juicing".
I would not go so far as to say "definate juice", but it is not uncommon for 16-18 year olds to take steroids in high school.
It is easy for them to get juice, and most don't care about stunting their growth and are misinformed by their dealers. If he is juicing - he is too young and should stop.