He started out beautifully, then progressively got worse and worse, and then bad.
He could have used a trot pole coming in to help set up the crossbar. The inside distance was too short and way too short when he cantered in. I'm guessing he ended up sacrificing his front end over the crossbar in order to get his feet down as quickly as possible, and give himself as much room as possible to the progressively larger oxer.
A bit too many repetitions of the same thing over and over for a youngster in my opinion, especially something that seems to encourage a deteriorating style.
That speedbump of a crossbar isn't really preparing him for the big oxer - even if the distance inside was set correctly. Give him a couple of fences to establish that rhythm, each one building upon the prior - trot pole & crossbar to 2'9" vertical to 3'3" vertical to big oxer. Pay attention to what the exercise is doing to his form and adjust as needed.
I really, really loved his first couple times through - but some of the ending ones, especially over the crossbar, were classic examples of an "unsafe" jumping style and you surely don't want to encourage that.