Try calling the school and asking for the PTO or PTA president. I get calls at work from people who contacted the school and the secratary routes them to me. If they can't give you thier number they can at least take a message and put it in the PTO/PTA mail box.
Another suggestion is to type up a flyer and send it to the schools. Address it to Principal/PTO president if the principal is not interested they may pass it on to the PTO.
We are a Boston based Dance Company who have an Elementary School Assembly Performance called "How to Watch a Dance Performance" We have been contacting schools to book some performances, but are realizing that going through the principal is not necessarily the most direct route to the powers that hire groups for assembly shows. Do you have suggestions about who to contact, how, and where? (Just in case you are interested in us for your own school, please visit us at digbydance.org) Thank you for all of your help!