You need to let your HT sort this out and trust her to do so. You might well leave, but what about the person who takes your place? What about the rest of the staff who are also complaining, but didn't have the foresight to keep a record? What about the children in the classes he is teaching, your leaving won't help them? You need to just trust your HT to do what is best, it is why they get paid more than us! Best of luck!