Five months after the Ohio Supreme Court upheld the constitutionality of the state's charter-school program, another teachers union is challenging the tax-funded, privately operated schools.

The Ohio Education Association filed suit in Franklin County Common Pleas Court yesterday on behalf of the Dayton school district. It accuses state Superintendent Susan T. Zelman, the Ohio Board of Education and the state Department of Education of failing to properly monitor charter schools.

Charter schools have violated state laws and various terms of their sponsorship agreements, yet few face any consequences, the suit alleged.

As a result, charter schools are undermining Ohio's education system by diverting tax dollars from traditional public schools.

"There is no reasonable justification for Ohio's public education system to benefit a few while harming the many," the 31-page suit said.

Dayton has the second highest number of charter-school students in the nation: nearly 6,500, or 28 percent of the district.

The exodus of students cost the district an estimated $43 million in lost state aid during the 2005-06 school year. Since 2000, $189 million has followed students leaving Dayton schools for charters.

"The expense of operating the Dayton City School District does not decrease in direct proportion to the reduction in its student population resulting from students who transfer to community schools," the suit said.

Department of Education spokesman J.C. Benton declined to comment, saying he had not seen the lawsuit.

"Ohioans have the right to expect the (state) to monitor the performance of the $500 million-a-year charter school program," said OEA President Gary L. Allen. "Through this legal action, we hope to end a pattern of lax state oversight, poor compliance and avoidance of fiscal and academic accountability."

The case was assigned to Common Pleas Judge Beverly Pfeifer, with trial set for April 15, 2008.

In a 4-3 decision in October, the Ohio Supreme Court upheld the state's charter-school law. The Ohio Federation of Teachers filed that suit, arguing that charter schools violated the state's constitutional requirement of a "thorough and efficient system of common schools" because they were not held to the same standards as traditional public schools.

The court's majority found the General Assembly had the latitude to set different standards for different types of public schools.

ccandisky@dispatch.com