Alleging that Pennsylvania's education-funding system is "irrational and inequitable," a group of parents, school districts, and organizations on Monday sued the commonwealth, saying it had failed to provide all students with an appropriate education.

Plaintiffs in the long-expected suit, filed in Commonwealth Court, include two Philadelphia School District parents and the William Penn School District in Delaware County.

State officials have "adopted an irrational school funding system that does not deliver the essential resources students need, and discriminates against children based on where they live and the wealth of their communities," say the plaintiffs, who are represented by the Public Interest Law Center of Philadelphia and the Education Law Center-PA.

Urban, suburban, and rural districts are included in the long-anticipated suit, which names as respondents Gov. Corbett, acting Education Secretary Carolyn Dumaresq, and legislative leaders.

"We believe that as a school district, we help our schools best by working with the governor and legislature. We unequivocally advocate for a formula that will fully and equitably fund the schools in our city and across the commonwealth," the district said in a statement.

"The Pennsylvania funding commission was formed to improve on a status quo that is painfully inadequate for our students, and we look forward to its results in conjunction with our continued efforts in Harrisburg."

Besides William Penn, the plaintiffs include the Panther Valley School District in Carbon County, the School District of Lancaster, the Greater Johnstown School District in Cambria County, the Wilkes-Barre Area School District in Luzerne County, and the Shenandoah Valley School District in Schuylkill County.

The state NAACP and the Pennsylvania Association of Rural and Small Schools filed on behalf of their members.

While leaders impose academic standards on children, they do not give them the resources to meet those standards, the suit states.

The state knows how much it must spend to educate all students fairly, but has failed to provide the money, said lawyer Michael Churchill of the Public Interest Law Center of Philadelphia.