Harman - this is exactly why I said it was important to start writing before and after each meeting.
You need to have all of this well documented so that you are not accused of things that you didn;t say and being aggresive when you have not been.
Letters are much easier to communicate with in terms of making sure the tone and content is not misunderstood - please, please, please start writing now!
Write to the head this morning, express your disappointment that things have escalated and have not been dealt with very professionally and request an early meeting with her to start to explore how the situation can be remedied. Then hand drop it off to school at lunch time.