Good question, because the same problems adults have, kids have and the chairs don't fit them as well in the first place. You want the back straight, feet able to touch the floor and the keyboard height not to high. I bought a desk for my son's computer yesterday and the tag said it was an ergonomic desk. The best type of clinician for ergonomics generally would be a psychiatrist or a physical therapist. I am not sure if athletic shoes are considered flat.
Shoes make a big difference, coupled with posture too.
If a woman has back pain, they should definitely stay off high heels. Once you have pain, you tend to splint, you won't be as stable. To then add the heel makes you more vulnerable to more injury. First, are children prepubertal or postpubertal. If young, then back pain is more often considered worrisome.