Narrow his grip and cue his elbow position.
Hello Mr. Rippetoe,
I came across this video of one of your gyms. I had a question about this kid's elbows. I've noticed the same high up elbow position with a few people (mainly my own son) that I have attempted to "teach" the squat too. How would you go about fixing his elbows as he squats?
Thank you!
Elbows in the squat - YouTube
Narrow his grip and cue his elbow position.
The way his elbows drop down as soon as he's upright seemed to indicate he's rounding his upper back ("chest up" cue), but if you look at it closely that's not true - the upper back looks straight throughout. So I think he's simply pushing his elbows up as he goes down. A good cue is to "pin" or "glue" his elbows to his torso before descending. Also, double check that the bar isn't ever so slightly too low, perhaps it's rolling and he's trying to prevent it from rolling down. He should be able to tell you if he feels the bar rolling.