Illinois is a state whose constitution specifies it offers a "free education." In looking through various cases from around the country, this is often what the courts examine when deciding if a school may charge extra fees for school services. While those cases are sometimes as minimal as an activity fee, they have even included districts charging for certain core items such as textbooks. As a "free education" state, Illinois was squarely within the "no pay-to-play' camp. Nevertheless, in a recent and (so far) unpublished appellate court decision, Illinois permitted the addition of a $350 fee for driver's education.
I imagine that as the financial pinch continues to be an issue that there will be more and more programs for which districts around the country will seek contribution from participants. If the courts in "free education" states permit it, how much more do you imagine those without that provision will allow.
Of note, Pennsylvania's constitution does not specify that districts must offer a "free education" and there are some districts in PA that charge for some non-core and extra-curricular activities already.
The Illinois case can be found now at Sherman v. Township High School District 214, 2010 WL 3834544 (sorry, although it may be available through some free service, I could not find a link to it except through westlaw).