Incorrect It is incorrect because his neck is tilted and that causes neck pain which he has been in technology class for a while.
Correct He is sitting correctly because he is sitting straight and isn't leaning in to cause back pain and his feet are on the ground.
Incorrect This kid is sitting incorrectly because he is sitting in the chair with his legs in the chair. That is putting a lot of pressure on his legs and could cause a lot of leg pain. His neck is sideways which causes neck pain after a while. He is also leaning in closer to the computer which will cause back pain over time.