When public school letter grades are released on Tuesday, it will mark the end of a generous scoring system sparked mostly by the tougher academic standards known as Common Core.

The policy, which morphed from two to four years, requires a curved system in how the state rates the effectiveness of about 1,400 schools. That means the highest-scoring schools would get an A and the other schools' scores would be distributed proportionally. The distribution of schools rated A, B, C, D and F cannot change from year to year.

But all that ends after the 2016-17 grades are announced on Tuesday at 11 a.m.

Gary Jones, president of the state Board of Elementary and Secondary Education, said using a curve distorts the normal distribution of grades.

No such grading plan will be used starting with the current school year.

"It is a more accurate picture of actual performance," said Jones, who lives in Alexandria.

The curve was supposed to be limited to two school years — 2013-14 and 2014-15.

Under the plan, the allocation of grades would not vary from the 2012-13 results, the second year the grades were issued.

BESE took the action in 2014 amid fears that, without a soft landing, grades for students, schools and districts would plummet when the Common Core-inspired rigor for reading, writing and math took hold.

The state panel in 2015 extended the curve another year — 2015-16 — because of pleas from superintendents and others. In 2016 the Legislature extended the curve for a fourth school year — 2016-17 — as part of a deal between advocates of major changes in public schools and backers of traditional classrooms.

BESE ended the policy in March, and panel member Jim Garvey, of Metairie, sparked controversy when he said then the state had been lying to parents about the value of the grades.

Even with the tougher rules, Garvey said Friday, about half of schools will be rated B and above in a state routinely ranked near the bottom nationally in academic achievement.

"We have a lot of 'A' schools that other states would consider 'B' and 'C' schools, a lot of 'B' schools that other states would consider 'C' and 'D' schools and so forth," he said.

State Sen. Conrad Appel, R-Metairie, a member of the Senate Education Committee and an early supporter of the grades, criticized the use of a curve.

"We have been doing a disservice to students and to their parents for a long time by curving the grades," Appel said. "It doesn't give them a fair representation of actual performance."

Brigitte Nieland, who follows public school issues for the Louisiana Association of Business and Industry, said the curve was not aimed at helping students. "I think we play a game, and the game is for the benefits of the adults, not for the benefit of students and families," Nieland said.

The announcement on Tuesday will mark the seventh time that the grades have been issued.

The grades largely measure how students fare on key tests.

The initial report six years ago showed that 44 percent of public schools were rated D and F.

Former Gov. Bobby Jindal used those results to help push through sweeping changes in public schools in 2012.

Critics have long charged that the annual marks are misleading, and many still question their validity.

Scott Richard, executive director of the Louisiana School Boards Association, said questions remain on the reliability of the tests and how school performance scores, which determine grades, are calculated. "And right now I don't think the average person can explain what the department is doing to arrive at those letter grades," Richard said.

"The curve I think from the professional educator standpoint was to give districts some level of assurance that the calculations were even in the ballpark in truly measuring achievement or not," he said.

Barry Erwin, president of the Council for a Better Louisiana, backs the move away from a curved system.

"The point of having a letter grade is to know what is going on in schools," Erwin said. "It will give us more transparency and a more accurate look at how our schools are doing."

Ending the curve is just one reason why Tuesday's letter grades will be the last of their kind.

Last month BESE approved a plan that will make it harder for students to earn an A.

The number of F-rated schools is expected to rise 57 percent next year, and those with A ratings are expected to fall by 38 percent, according to calculations by the state Department of Education.

Follow Will Sentell on Twitter, @WillSentell.