Lawmakers in Ohio approved on Thursday major changes that will affect how the state evaluates success in Ohio schools.

The Ohio House of Representatives approved House Bill 555, which would grade schools on an A-F scale instead of the current, excellent-academic emergency scale. The House passed the bill without amendments in a party line vote, 58-27. The bill now heads to the Senate.

Under the bill, schools and school districts would be assessed on 15 performance indicators such as standardized test scores and graduation rate and assigned a letter grade beginning with the 2014-15 school year. Until then, schools would be graded on some of the indicators but not given an overall letter grade.

Democrats said the new system is unfair to schools that are already dealing with a bevy of reform measures including a shift to the tougher Common Core curricula.