Second Koing on keeping the back/ass down throughout the lift. I'm guessing he may be a taller kid? That was a major sticking point when I started. Although he's on the right path starting at such a young age.
Also it seems he is tightening his shoulders and starting to shrug before he hits his explode position. Drill it into him to keep his shoulders and arms (but not hands) relaxed until he hits his explode. Otherwise he'll have worse bar position during the catch along with a weakened velocity after the second pull.