YANBU, that's sweet.
But there is working and working.
I'm at school from 8am until 11pm today. This happens about twice a week and some weekends. I probably work an average of 75 hours a week in termtime.
But:
a) I'm 'at work' but currently sat on my arse on mumsnet
b) come school holidays I work an average of about 2 hours a day!
SO, before you thank your teacher, consider than she might be a lazy bum like me who is technically present but ... yes, on mumsnet! And who then checks out for the holidays.
But she might not be. She might work very hard!