So sorry to hear about these troubles. Speaking as a fairly recently departed - and now somewhat jaded and cynical - parent, I'm sorry to say that this situation is not all that uncommon, and you would find much the same occurring in vocational training everywhere. Some will sail tharough the whole thing and will have nothing but praise for the school, the training and the staff. Others, training there at exactly the same time and in the same class, will tell the opposite story.
The favourites (and occasionally also the moneybags overseas ones) get all the attention, all the extra coaching, all the support they could possibly need if they get injured or are suffering emotional difficulties; they are encouraged to enter competitions, they are handed principal roles in school shows, and are given opportunities galore.
The middling also-rans are pretty much ignored and are treated as cash cows, and corps fillers for performances. The ones who fall behind (for whatever reason) don't get the extra support and coaching they would benefit from, and really need and deserve. They are metaphorically thrown on the scrap heap and pretty much written off from then on.
There seems to be a culture among some staff of... well... not institutionalised bullying as such, but more of an attitude that the professional dance world is brutal, and these students need toughening up if they are going to succeed. It is a case of survival of the fittest, and it is the school's job to weed out the ones who are going to break, either physically or mentally. Some of the students are treated appallingly, yet they are afraid to rock the boat, to complain or make any kind of fuss, in case it jeopardises their position, either to continue training at the school, or that word will get out that they are 'difficult' and they will never get a job. The ballet world is a very small one. Nobody wants to stick their head above the parapet. They have too much to lose. And we are talking about young people under the age of 18 here, who may be living far away from home for the first time, and have no-one to turn to when they need help.
As parents we put our trust in these schools to do their best to nurture our young dancers, and we put our faith in the belief that the schools will take care of them and have due regard for their welfare and well-being.
I can't tell you how much it hurts to have that trust betrayed, and to have your young dancer's love of dance destroyed, and their aspirations and future career ruined.