Now that the state Supreme Court has revived a lawsuit challenging the inequitable way Pennsylvania funds its public schools, the issue needs to be resolved as quickly as possible.

One of the arguments made by opponents to efforts to put more state money into public schools is that Pennsylvania already spends enough to educate its children.

It's a lie.

The conservative Commonwealth Foundation likes to cite a National Center for Education Statistics survey, which ranked Pennsylvania ninth in the nation in funding public schools, at $16,627 per-student.

But that average is skewed by the higher amounts rich school districts can afford to spend on education.  Lower Merion, for example, supplements its state funding with about $24,369 per student raised through local property taxes.

Equity is the primary goal of the school-funding lawsuit. No one expects absolute parity, but the degree to which a child's zip code determines the quality of education received is too great.

The plaintiffs rightly contend that the state's constitutional duty to provide "a thorough and efficient system of public education" means it is responsible for reducing the funding gap between rich and poor schools.

The state knows what it needs to do. It devised a school funding formula in 2015 that allocates funding based on criteria such as how many students live in poverty, how many students are learning English as a second language, and the local community's ability to raise taxes for schools.

But the formula has only been applied to new basic education funding, which amounted to only $352 million out of $5.9 billion in the 2016-17 education budget. The formula should be applied to the entire basic education budget. Poorer schools need a larger share to handle the bigger challenges they face.

Beyond the issue of equity, Pennsylvania needs to increase the total it spends on education. It ranks 46th nationally. This year's $6.1 billion education budget may appear to restore the cuts to K-12 funding made by Gov. Tom Corbett in 2011, but taking inflation into account an additional $911 million would be needed to do that.

Since the Republican-led legislature isn't willingly to meet that responsibility — despite polling showing Pennsylvanians want it to — the courts need to resolve the matter. And the sooner, the better.

This case has been pending since the original lawsuit was filed by the William Penn School District and others in 2014. Last year, the state Supreme Court ruled the judiciary could review school funding, typically a legislative duty, and sent the case to Commonwealth Court.

And this week, Commonwealth Court overruled an objection by state legislative leaders that there was no merit to the plaintiffs' claim that the current funding system harms students.

If the courts need inspiration to do the right thing for schoolchildren, the judges need look no farther than across the Delaware to New Jersey, whose Supreme Court in 1990 ruled the state had an obligation to increase funding to poor school districts.

The cases aren't identical, but there are enough parallels to provide lessons. The main lesson is that everyone in a state benefits when its public schools successfully teach children who grow up to become productive, law-abiding, taxpaying adults.