This is a sticking point with many a booster group around me in PA. and I fully understand that a booster group may want to stay outside of Board umbrella and sticky fingers---Locally the debates over which booster club gets to run the food concessions at ball games sometimes takes longer than a discussion about a $ 20 million construction project.
If you want to be under the school umbrella as an official sanctioned booster group you probably need to play be school board rules. Locally to be sanctioned has the added benefit of putting you under the Boards liability coverage
If you operate outside the school umbrella you are free to suggest that school board go pound sand. The coach might be instructed by his superiors to break off contact with you.
In terms of fund raising unless you have independent 501c3 status you might want to reconsider operating under the Board sanctions.
Locally we have one major booster group that operates inside the Board umbrella and does not have 501c3 status on its own--and egually large one has its own 501c3 letters and PA state registration and somehow manages to have its feet both in and out.
A significant local fund raiser probably needs registration with PA Charities Bureau if not under Board umbrella
From a donor standpoint it may be easier to induce donations if its to a proper exempt group --the tax deductibility is safer and it might be easier for hard booster workers to address personal deductible expenses if its to a valid exempt entity.
But I do understand not wanting everybody else to get into your financial pants.
Don't laugh --I can see times comming where its the boosters group task to provide after school academic assistance for varsity athletes so as to maintain eligibility and the school will pick which kids need help --we've been close --and only certain minorities need apply----and if the boosters are more active to support traditionally boys sports and traditionally girls sports falter due to lack of outside support --be careful --not politically correct!