Charter-school administrative expenditures are nearly double those of conventional public schools, and their highest-ranking officials are paid far more.

They spend less on instruction than school districts, but more on support services and facilities.

And while charter-school enrollment has jumped significantly over time, payments to the schools are far outpacing their actual rates of growth in admission.

All that is according to a report on Pennsylvania's charter schools issued Thursday by the Pennsylvania School Boards Association, made up of nearly 4,500 school board members.

In a 35-page study that came after rounds of records requests during the last 15 months, the conclusions present a broad picture of Pennsylvania's 173 charter schools, which have become part of an ongoing national debate about what effect the charter-school movement is having on traditional public schools.

"This is not intended to be any sort of an attack on charter schools," said Andrew Christ, education policy analyst for the organization, during a conference call Thursday.

But, he said, "charter schools need to be held to the same standards of accountability and transparency as traditional public schools."

Charter schools in the Keystone State and across the country have been growing rapidly. They also have been beset with criticism, mostly from proponents of traditional public schools.

Receiving the bulk of their revenue from districts - in Pennsylvania, nearly 84 percent - charter schools' critics have argued that using taxpayer money for charters has taken funds away from conventional schools.

Charter-school advocates have countered that charters provide more choices for families, and can increase learning opportunities and encourage innovation.

To analyze information on charter revenue and expenditures, the association filed records requests with all charter schools across the state. The association received information from nearly 85 percent.

According to the report, tuition payments to charters accounted for about 5.4 percent of all statewide school district expenditures in 2014-15. However, some districts in the area have felt the squeeze more than others.

In Delaware County's beleaguered Chester Upland School District, which has operated under receivership for four years, nearly half of its expenditures were allocated to charter-school payments, the report stated. In the Philadelphia School District, slightly more than one-quarter of its expenditures went to charter schools.

Focused largely on how money flows out of school districts and into charter schools, the report highlighted the disparities in spending between the types of schools - including special-education costs. It found that charter schools were overpaid for special education by nearly $100 million in 2014-15.

The report also called for a greater level of oversight by the Pennsylvania Department of Education.

"Charter schools are public schools," the report stated. "However, charter schools are not held to the same standards as other stewards of public tax dollars when it comes to transparency in operational and financial decisions."

In a response Thursday afternoon, the Pennsylvania Coalition of Public Charter Schools said that while it had not examined the report in detail, it took exception to some of its recommendations, including one for charter schools to be more open about their operations.

"Charter schools are already subject to the same accountability and transparency laws as district schools," the organization said in a statement. It said that despite some opposition from the school boards association, the legislature has been working to pass legislation that would increase charter school accountability.

Beyond analyzing payments to charters, the report focused on the differences in expenditures between district-run schools and their charter-school counterparts. On average, the report stated, charter schools allocated a greater proportion of their budgets to administrative costs - about 13.3 percent - including support personnel, building services, and maintenance. Conventional school districts spent about 5.6 percent of their budgets on administrative costs, it said.

In addition, the association reported, charter schools are spending about three times more per pupil on top administrative salaries.