Public schools are supposed to be free. But faced with budget cuts, rising staff costs, and declining tax revenues, many are instituting "pay to play" fees, charging students extra for everything from electives to after-school sports — and even some required classes, like French and basic sciences. Here, a brief guide, by the numbers, to these "controversial" fees:

Course supplies fee for students taking English 9 at Dakota Ridge High School in Littleton, Colo.

Fee for students taking Honors English 9

Course supplies fee for students taking French IV at Lakota Local Schools in Liberty Township, Ohio

Registration fee for students in the Community Unit School District 200 in Wheaton, Ill.

Extracurricular activities fee for students to participate in activities like the literary magazine, National Honor Society, and/or Students Against Drunk Driving in the Lenape Regional High School District in Shannon, N.J. With such resume-enhancing activities coming at a cost, "administrators and parents... worry that fees might affect some students' chances of getting into good colleges," says Stephanie Simon in The Wall Street Journal

Extracurricular activities fee for students who play football at Hamilton-Wenham High Regional High School in South Hamilton, Mass. 

Cost of one year of public education for the Dombi family's four children in Medina, Ohio. The cost includes fees for basic courses like Spanish I and Earth science, extracurricular activities like cross-country and track, and the cost of graded electives, like band.

Amount on top of that the Dombis paid in property taxes earmarked for schools that year

Number of years in a row that Medina residents have voted against raising property taxes to stave off cutting arts and athletic programs in schools

$17 billion
Amount states have collectively cut education funding by in the past two years, though some of the cuts have been buoyed by the federal stimulus

Average percentage increase in spending per pupil, after adjusting for inflation, over the past 20 years

Percent of the expenses devoted to personnel costs in many school districts

Percent increase in the average salary for public school teachers, nationwide, since 2001. "That growth didn't quite keep pace with inflation," says Simon.

Sources: Wall Street Journal, Los Angeles Times, Atlanta Post, Huffington Post