Charter school advocates and the Philadelphia School District have long been at odds on the cost of charter schools.

For the first time, Michael J. Masch, the district's chief business officer, said yesterday he had completed a detailed financial analysis to come up with an amount: $105 million for the 2008-09 academic year.

One key reason is that 27 percent of the children attending charters were previously home-schooled or attended nonpublic schools.

"Funding charter schools has become a very significant element in the school district budget," Masch said during his presentation to the School Reform Commission on the net costs of charter schools.

The 63 charter schools in the district enroll 34,400 students. The school district's $2.3 billion budget for 2008-09 includes $320 million for charter schools, a figure that includes all costs, even those that are reimbursed from the state.

Charter schools are independent, taxpayer-funded schools that are free from many of the requirements facing traditional public schools. This academic year, the district is paying $8,088 in charter tuition for every student in regular education and $17,658 for each student requiring special education services.

"We are one of the leaders here in Philadelphia in supporting the charter school movement," Masch said. "But the way in which charter schools affect the finances of the district and how they are funded, we found, is not well understood."

He determined the $105 million cost to the district after analyzing both the savings and extra costs related to charters and factoring in state reimbursements for a portion of charter costs. The state reimbursement rate, which is based on the previous year's enrollment, increased from 28.3 percent in 2007-08 to 36 percent this academic year.

Masch said the district saves some money for teacher salaries and school materials as a result of students who transfer from district schools to charter schools. Overall, he said, the net cost to the district for each of these students is $1,719.

But he said district data show that slightly more than 27 percent of all students in city charters entered from nonpublic schools or had been home-schooled. As a result, he said, the district is paying to educate them for the first time. The net cost to the district for each of these students is $5,707.

While there are many reasons why the district has charter schools, including providing parents educational choices, Masch said his analysis dealt strictly with their finances.

The number of charter schools has grown from four in 1997-98 to 63. The School Reform Commission has given provisional approval to seven more charters to open in 2009-10, provided the district's budget has sufficient funds.

Lawrence F. Jones Jr., president of the Pennsylvania Coalition of Charter Schools, questioned the district's commitment to charters. He also asked questions about Masch's financial presentation, including whether the charter school community had reviewed his analysis.

He said he hoped his questions would "help clarify the current and future status for charter schools."

The commission did not respond directly to Jones' questions. He said the coalition was eager to help "find answers."

In other action, commission chairwoman Sandra Dungee Glenn and superintendent Arlene Ackerman said the district would explore how it might be able to assist children and families coping with the cutbacks in programs Mayor Nutter announced last week, including the closing of libraries and recreation centers because of the city's budget crunch.

Contact staff writer Martha Woodall at 215-854-2789 or martha.woodall@phillynews.com.