By Mike DeNardo

PHILADELPHIA (CBS) — The Philadelphia School District says its system of rating schools is flawed and it’s looking for an outside firm to fix it.

The district’s 1-to-10 rating (1 being the best, 10 the worst) allows parents to compare schools, but it also had been a factor in deciding which schools should be overhauled or closed.

Deputy Superintendent Paul Kihn says a review found internal mistakes made, in how test scores and other data were calculated to come up with the School Performance Index (SPI).

“All of the underlying data is completely accurate. And the mistakes that were made are at the level of the way in which we calculate the single-digit score.”

Kihn says the district is now looking for an outside firm to re-compute the SPI.

“We actually don’t know how widespread or how significant the mistakes were in terms of how the numbers are going to come out.”

Kihn says academics will be considered but the SPI will not be used, as the district identifies several dozen more schools to close next year.