It is very common for young players to develop poor technique in their shot, because they are over compensating for not having the strength yet to get the ball to basket. One common development is pushing the elbow outward instead of keeping it underneath the ball, or shooting from behind the head.
My approach is to not over emphasize pure mechanics at a young age, because a shot can be fine tuned later. I never want to become discouraging. Instead, I emphasize learning the discipline to take shots everyday (practice, practice, practice), and becoming a student of the game and one's own fundamentals development. In my opinion, in the end, practice and repetition can outweigh unorthodox shooting form: Vinnie Johnson, Larry Bird, and Lonzo Ball all come to mind.
Carter has a few quirks we are working through. There are four important concepts that I have him focus on at his age:
1. Wide stance with bent knees, being ready to shoot.
2. Keep the elbow underneath the ball. This is still difficult, especially the further he gets away from the basket. We always start in close, and I do my best to keep him there :) .
3. His release alternates between a pushing the ball up, and properly releasing the ball off the fingertips. I emphasize this by asking him to 'flick' the ball, rather than push ... overdo the backspin.
4. Making sure his weak hand is used as a guide, not as part of the shot. To help with this, we use a shooting paddle.
Perhaps one of the most pure jump shooters in modern basketball is Klay Thompson. Below is a great video that I've shared with my son as we work to repair some of the poor habits he has created.
As Klay demonstrates ... the combination of form purity and practice repetition is the real sweet spot.