Public school letter grades could not plunge during a two-year move to the Common Core academic standards under a bill that won approval Wednesday in the Louisiana House.

The grade freeze, which was in the form of an amendment to House Bill 953, cleared the House 50-41.

Moments later, the bill passed the House 63-33.

The proposal is aimed at softening the impact of the national tests that go with Common Core, which is set to take full effect for the 2014-15 school year.

Under current plans, the impact of the exams would be eased for the current school year and the 2014-15 school year.

The legislation would add another school year, 2015-16, to the schedule.

House Speaker Pro Tem Walt Leger III, D-New Orleans and sponsor of the bill, said it would give students and teachers time to prepare for the new standards in reading, writing and math.

The bill initially called for a curved distribution of grades in 2014-15 and 2015-16.

That means the total number of A, B, C and other grades would not vary overall, but could go up or down at individual schools compared with the 2012-13 school year.

Backers said that would prevent school districts and individual schools from unfair setbacks during Louisiana’s move to Common Core, which has been adopted by 43 states.

But House Democratic Caucus Chairman John Bel Edwards, D-Amite, successfully sponsored an amendment that says a school district’s letter grade could not drop during the two-year period.

Grades would be allowed to rise if warranted.

Public school letter grades are designed to give taxpayers a clear picture of how schools are faring.

Teacher unions and other critics have long complained that they often offer a distorted picture of educational performance.

Edwards noted that some schools plan to administer tests with computers and others with pencil and paper, which he said is another reason to require a near freeze.

Leger opposed the change.

He said HB953 addressed the issue by requiring a curved distribution of school and school district results.

The measure next faces action in the state Senate, where it faces an uncertain future.

Senate Education Committee Chairman Conrad Appel, R-Metairie, whose committee likely will review the bill, sponsored the 2010 law that required the state to assign grades to schools and school districts.

Appel is also a supporter of Common Core and the test plans set to go with it.

State Superintendent of Education John White criticized Edwards’ amendment.

“You want to provide some level of accountability to the parents,” White said.

In remarks to the House, Leger pitched his proposal as one that would continue the state on its path to national academic standards while also giving school officials adequate time to prepare.

The state Board of Elementary and Secondary Education earlier approved a two-year moratorium on the impact of Common Core exams.

The freeze approved Wednesday also would apply to the use of controversial data during teacher evaluations.

Students in grades three through eight are scheduled to take Common Core exams produced by a consortium called the Partnership for Assessment of Readiness for College and Careers.

However, those plans also face legislative fire.

Leger has described his bill as a middle ground between Common Core backers and critics.

However, the plan has sparked criticism from backers who oppose additional delays to the assessments and opponents who contend the bill does not go far enough.

Public school students are in the midst of Common Core test trials before they take them in earnest next year.

Backers of the new standards say they will improve student achievement.

Opponents call them top heavy with federal interference and without enough parental input.