I think it's excessive. It's not fair to children to tell them you'll lose your job unless their parents support the school budget.
As for paying for supplies...I spent a great deal of money this year on school supplies for DD. We are required to supply notebooks, pencils, erasers, crayons, markers, folders, etc. as well as antibacterial wipes, kleenex, cups, and the like. And this is just first grade. All parents get a list of required supplies at the beginning of the year and reminder notes when the children run low during the year.
The teacher also sent out a note at the beginning of the year asking for extras like stickers, stamps, colored paper, etc. to keep school budget costs down. She continues to do this throughout the year. Just yesterday I got a note asking for 2 boxes of assorted types of bandaids for a math project they are doing.
DD is in first grade and so far this year I've spent almost $200 on school supplies for her and her teacher. That doesn't count all the goofy school fundraisers and scholastic book orders (which are almost mandatory because they get sent home with a note saying that the more books you order, the more books she can purchase for the classroom and without my order, her ability to buy for her classroom will be lessened "dramatically") as well as the cost of the school fieldtrips and holiday art projects.
My understanding from other parents is it gets worse as they get older because you need more supplies per child. UGH!
In our town we pay extra for bus service and most all sports and afterschool activities so the school budget can be used for curriculum.
So to pay taxes for what I'm assuming is partly for education, to supplement it with paying for the bus, all extra-curricular activities, school supplies for the child, school supplies for the teacher, and other miscellaneous expenses related to the lessons developed by said teacher for the curriculum, it's a bit offensive to have your child come home and say you need to pay more or my teacher is going to lose her job.