To find out if your organization is a 501(c)(3) listed with the IRS, you'll need to contact the them. An online lookup page is available at
www.irs.gov/charities/page/0,,id=15053,00.html
The phone number for the IRS Exempt Organization customer service toll-free line is 1-877-829-5500. They are generally very helpful. Finding out your
status is key.
Now, if you are interested in whether or not your a
corporation, that would be handled at the state level. Since we can't tell what state you are from, I can't direct you. But you should be able to do a web search and discover what state agency governs incorporation of non-profit organizations.
As far as the principal - he may well have the power to control what organizations are officially recognized by the school, which are allowed to use school resources, and even the school name. Finding out if you are set up as an independent entity is certainly a good step, but that alone will not solve your problems. While it's technically possible to operate completely separate from the school, it would be very difficult to be successful without official recognition and cooperation.