I know how you feel. I have always thought of young students not knowing exactly what they really want. They may hate it now, but when they are older they will be happy they did it. I have taught many students who are 50 years + who decided that it was now time to go back to the piano after giving up on it when they where a child. ALL of them tell me how they regreted not playing the piano.
I have had students who are not interested in learning the piano and as much as my natural emotion tell me to dump them and tell them to get lost, I never have done this. I always teach them with excitement because I personally enjoy the piano. If they don't it doesn't matter because I am having fun trying to teach them. They may not listen, but then simply keep repeating the same command until they do listen to you or make attempts to.
Many of them stuggle to maintain concentration but this is all good, even if their piano output is poor, the fact that you can challenge them to focus for 30 mins or 1 hour that you teach them gives them useful Life tools. In school they have to learn to study when they don't want to, when they work in the workforce they have to realize that not everyone you meet will agree with you and not everything you do with be something you really want to do. You learn to deal with it and make progress with it.
Sure as music teachers we wish to teach music, but sometimes the students we get need life lessons and lessons in discipline much more than the piano lesson itself. Like kids who join martial arts classes. The teachers don't expect them to be grand masters or do things perfectly, the lessons about respect disipline etc, these things are more valuable, the school is just a medium to teach these life skills.