Have you been attending PTA meetings yourself? Have you been helping them with their current projects? If not, then you might not get much traction. If I’m the head of a volunteer organization, and my first communication with you is a letter telling me what I’m supposed to help you with, I’m probably not going to jump right to it.
You are more likely to get help if you participate in PTA meetings and activities, and talk one-on-one with other members about the issues that concern you.