Hi here is my friend that I'm teaching how to squat, the weights are starting to grind a bit. This was the 2nd back of set at 80 after failing 107.5 getting 4, 4. His back doesn't look right to me but I'm unsure how to que him properly.
YouTube
What do you think? Apart from getting shoes, which he promises he will.
This will go a long way toward fixing your friend's squat.
Identifying and Correcting Thoracic Spinal Flexion in the Squat | Bill Hannon