How many animal classes are there?

I don't mean classes as in the school. I mean Classes in the classification of animals, one of the levels of Kingdom, Phylum, Class, Order, Family, Genus, and Species. No website I know says exactly how many classes there are, and the closest I got to a specific number was "Around 100" and was talking about law school. I am frustrated that I cannot find one, though I have checked and searched through everything. Help!