charterchart02The city’s spending bill for charter schools next year is likely to surpass $1 billion, a 24 percent increase that exceeded conservative estimates offered by budget officials earlier this year.

In January, the Department of Education projected it would spend about $70 million more on per pupil expenditures for the growing charter sector, which will increase from 159 to 183 schools, in the 2013-2014 school year. That figure swelled to $210 million when Mayor Bloomberg proposed his executive budget last month, a gap that caught come city lawmakers by surprise.

“I find it totally outrageous and unacceptable that you could be so far off,” Councilman Stephen Levin said at Tuesday’s education budget hearing with department officials.

The total spending plan proposed for education is $24.9 billion, a 4.5 percent increase that includes $19.8 billion — a 3 percent increase — to pay staff and operate schools, and $4.9 billion — a 10 percent increase — for pension and debt expenses.

City officials said it’s not unusual for there to be a gap in projections between January and May budget forecasts, especially when it comes to charter school expenses. Enrollment for expanding charter schools still aren’t determined and some proposals for new charter schools aren’t finalized, they said.

“At that time, we still don’t know the full extent of how the charters are phasing in,” said Chief Financial Officer Michael Tragale. “That’s why some of the projections were off.”

In planning for this school year, for instance, the city initially said it expected charter school expenses to increase by $60 million, a figure that ultimately increased to $112 million when the executive budget was adopted in June 2012.

Despite the city’s miscalculations, the Independent Budget Office managed to make a more accurate projection. In a March analysis, the IBO noted the low-ball estimate in the city’s preliminary budget.

“IBO estimates that charter school payments will be significantly higher next year, totaling over $1.0 billion,” the report says.

The analysis also projected that by 2017 the number of charter school students will have grown to 120,000 and their costs will have exceeded $1.3 billion.

This year, spending is about proportional to the number of students in charter schools. There are 56,600 charter schools students, slightly more than 5 percent of the student population; their total projected costs in 2012-2013, $865 million, represents 4.5 percent of the operating budget.

Levin said the recalculations — this year’s adjustment was a 200 percent change — made it difficult to monitor charter school spending, which is determined in part by the state’s per-pupil funding formulas.

“I feel like by not presenting an accurate number at the preliminary budget, the Department of Education is getting around this committee, this council’s role in having oversight over the budget in the city of New York,” Levin said.

Tragale said that there would be more transparency in the future now that charter school spending has its own unit of appropriation in the budget. Previously, it was lumped into a $2.7 billion line item that includes payments for special education services for private school students and foster care students who have been placed outside New York City.

Speaking to reporters after the hearing, Chancellor Dennis Walcott said that charter schools, which tend to outperform district schools on state test scores but serve fewer high-need students, were a valuable school choice for parents.

“Obviously, there was a discrepancy, but the bottom line to me is more important: that these schools are educating our students and that’s the overall goal,” Walcott said.