Pennsylvania is failing to adequately fund public education and violating its constitution, the state’s top law enforcement official said Monday in a court filing endorsing a landmark lawsuit filed by school districts, parents, and statewide groups challenging the school funding system.

In the brief filed in Commonwealth Court, Attorney General Josh Shapiro said the constitution’s education clause — which requires the legislature to provide a “thorough and efficient” system of education — means that lawmakers must “ensure every child in Pennsylvania has a comprehensive and effective public education, one that reflects contemporary knowledge and which prepares students to succeed in a career and contribute to Pennsylvania’s civic life.”

“Despite the best efforts of the Commonwealth’s dedicated teachers and administrators, many Pennsylvania schools are not able to provide the level of education required by the Constitution — not for lack of trying, but for lack of adequate funding,” Shapiro said. “The consequences — students who lack proficiency in core subjects and the tools for success in life and career — rest at the feet of the legislature.”

A Democrat running for governor, Shapiro submitted the filing at the deadline for amicus briefs in the ongoing school funding case, which centers on claims that Pennsylvania’s approach to education funding is so inadequate and inequitable that it violates the state constitution.

Since the three-month trial wrapped up with closing arguments in March, both plaintiffs and the Republican legislative leaders defending the state — who argue the state already spends more than most on public schools, and say it’s the legislature’s role, rather than the court’s, to determine how much money to allocate — have filed lengthy briefs outlining the facts behind their cases and their legal conclusions.

Judge Renee Cohn Jubelirer will hear oral arguments on legal issues in July, with a ruling to come possibly several months later.

» READ MORE: Testimony in Pennsylvania’s school funding trial is over. What happens now?

Lawyers for plaintiffs — which include six school districts, among them Delaware County’s William Penn — said Shapiro’s brief bolstered their case.

“This is a big deal. The people of the Commonwealth know that Pennsylvania students deserve better, and that our state constitution demands it,” Dan Urevick-Ackelsberg, staff attorney at the Public Interest Law Center, which brought the case along with the Education Law Center, said in a statement. He said Shapiro “has made clear that our state legislature has failed to live up to this standard set by our state constitution, and that students have paid the price.”

Shapiro’s 62-page brief focused on the constitution’s education clause, and sided with plaintiffs in arguing that the court must consider student outcomes — and not just how much schools are spending — to determine whether the state is meeting its obligations.

“The court cannot actually evaluate whether our public schools are providing students with a comprehensive and effective education without looking to whether and what our children are actually learning,” he said in the brief. During trial, plaintiffs pointed to poor standardized test scores as a measure of the inadequacy of funding.

Shapiro did not appear to address a second legal claim from the plaintiffs — that given Pennsylvania’s heavy reliance on local taxes to pay for public education, funding is so lopsided in favor of wealthy school districts that it violates students’ equal protection rights.

His brief was not the only one submitted on behalf of plaintiffs. Five constitutional law professors from Pennsylvania law schools filed a brief that did address the equal protection claim — arguing that education is a “fundamental right” and that students are entitled to receive an education in a nondiscriminatory manner. Four other briefs were filed by education groups, business and higher-education leaders, and teachers’ unions.

On the side of legislative defendants, the conservative Commonwealth Foundation filed an amicus brief in January, arguing that the state already spends more than is required on education and that more funding wouldn’t necessarily improve educational quality.