A contractor analyzing results of a federal program that pumped a record $5 billion into failing schools inadvertently excluded data from some of the schools, forcing the Department of Education to scrap the analysis.

The contractor was asked to analyze how the targeted schools performed after receiving school improvement grants from the Obama administration.

The department made the initial findings public in November. It showed mixed results, with students at more than one-third of the targeted schools doing the same or worse in the 2011-2012 school year, after the schools received the funding.

But agency officials said Wednesday that they discovered that the analysis was faulty because the contractor had failed to include data from some schools. Officials removed the flawed analysis from the department Web site and said they hoped to have revised information in January.

It is unclear how many schools were excluded from the analysis, spokeswoman Dorie Nolt said. But she said her department does not expect the revised analysis to show significantly different results.

The American Institutes for Research (AIR) was paid $28,300 for the faulty analysis, according to Nolt.

The data are important to researchers trying to determine whether the heavy federal investment had an impact on the nation’s worst schools.

The Obama administration has handed out $5.1 billion to states to improve academic performance at about 1,500 schools since 2009, the largest federal investment ever targeted at failing schools.

A significant number of schools that received School Improvement Grants — as many as half — were intentionally excluded from the analysis for a variety of reasons, including that the data were missing, the schools were shut down or the state tests were changed, making it impossible to compare scores over time.

A large chunk of the grant money came from the American Recovery and Reinvestment Act of 2009. The School Improvement Grants had been part of No Child Left Behind, the 2002 federal law. But stimulus spending increased the budget for the grants sixfold.

Under the Obama administration, schools could receive up to $2 million annually for three years. Any school accepting a grant had to agree to adopt one of four controversial strategies: replace the principal and at least 50 percent of the staff; close the school and enroll students in another, better-performing school; close the school and reopen it as a charter school; or transform the school through new instructional strategies and other techniques.