You should also contact your state PTA office, they are able to give you lots of information on starting High School parent groups.
At high school the PTSA becomes a little different, with the many booster clubs doing fundraising, that portion of the work becomes less the focus. Programs such as the PTA's "reflections" arts program are very successful! Other PTSA/O's work on programs focusing on bullying, and school safety.
Some also run fundraising campaigns targeting specific needs such as technology.
High school is different because often our children do not want us "involved" in their school, they are spreading their wings. BUT that is why we need to be involved, and guide them to making good choices.

I believe you would run it the same way as an elementary, just your goals would be different. I know a lot of high schools don't have a pto because of so many booster clubs & groups through-out the school all fund raise. Is there enough parent interest to start with? You would to list your goals, by-laws at some point, EIN, eventually a 501c3. I hope this helps some. Good luck!! You can have a pto in the high school. Having the Principal's support is a great start.

Our high school has never had a pto, now the principal is interested. I am having a hard time locating info on organizing one, the activities that are being done, etc... So much info is vague. Help, but please be specific. I have worked for elementary and middle school ptos for 10 years, how does high school differ?