If you say dance is something that they 'really love', then how much disrespect did you give to the hobbies that you 'like'? It's such an insult to dance, you accept corrections but can't find it in you to change. 

Maybe it's because I'm an aspiring pre-professional (but my ambitions are delayed due to financial reasons), I may love dance more than you. But you don't need to have the passion of a professional to bring required items, show up on time during practice, be respectful to teachers... You lament when punishment is given, but get that in your mind that you deserve it. It was never unjust permission, and he have given you too much leeway. 

You tell me you wanted to leave because you think you had too much exercise (okay I can't translate the exact term) for the day. I say bull, what is wrong with you, your skills aren't up to par and you don't want to train further? Unless you really can't do it anymore, you hadn't had too much exercise. And he can tell if you have reached your limits. I'm sure you have never really loved dance.  

(I need to translate this in Chinese... and try to lash at them with my not-so-good Mandarin, but it's time they change.)