Tim Carter, president of the State Board of Education, explains the apparent problems in the new grading system.

School letter grades will remain in limbo after the Arizona State Board of Education voted Monday to extend the timeline for appeals and create a separate committee charged with proposing revisions to the new grading system.

Amid a chorus of concerns from schools, the board officially dubbed the new A-through-F school letter grades “preliminary” — retroactively approving a decision Board President Tim Carter made unilaterally just before the final grades were supposed to be issued to schools earlier this month.

Of the roughly 1,700 Arizona schools that received letter grades, nearly 200 are still under review or appeal — though that number will likely grow as more schools formally appeal their grades under the extended appeal deadline of Nov. 3.

By opening up the formula to a separate “technical advisory committee,” the board left the door open to changing grades that are not being appealed or reviewed.

But board members cautioned that after spending a year coming up with the original formula, they didn’t want the technical advisory committee to go back to the drawing board.

Calvin Baker, the superintendent of Vail Unified School District and a member of the board, said he wanted the committee to review the problem areas, not the entire formula.

“We’re not suggesting this whole process has to start over from the very beginning. There’s a lot of good work that’s been done,” he said.

The board identified three major areas of concern that need to be addressed immediately, while leaving the door open to more dramatic changes to the formula, possibly impacting this year’s school grades.

“I’ll just plant the seed that at some point in time, there may have to be a very serious discussion about changes, and what years those changes apply. Are we talking about (school year) 2016-’17, ’17-’18, ’18-’19?” Carter said.

The most widespread problem is that more than 100 grades were withheld because of nontraditional grade configurations, such as schools that offer sixth through 12th grades. Because K-8 schools and high schools are graded on different criteria, schools with unusual grade configurations were befuddled about how their grades were calculated.

The board offered several fixes to address that issue, including creating a unique model for each grade configuration, taking the higher of the two scores or averaging the two scores. Ultimately, the board decided to wait for input from the technical advisory committee before making a decision.

Other schools complained that the data the Arizona Department of Education used to calculate their scores were inaccurate, or that the data were correct, but due to coding issues produced inaccurate scores. The latter would be more problematic, board members noted, as the board would likely have to recalculate every school’s grade to ensure accuracy if coding errors were found to be the culprit of the problem.

Finally, the board still needs to decide how to deal with more than 70 schools that appealed their grades and those that might file under the extended deadline. Schools were originally told that only tornado-like events would qualify them for an appeal, though after hearing about the data issues, the board decided to take a more inclusive approach to appeals.

But the board also gave the technical advisory committee a broad mandate to review “any problematic problems” within the formula and make recommendations how the board should address them before issuing final letter grades, which the board now hopes to complete by January.

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Charter schools, especially typically high-performing ones, have been among the most vocal opponents of the new grading system. They’ve argued that the formula’s emphasis on student growth means schools that already have high-performing students are penalized, and that that component of the grade formula needs to be revisited.

Sherry Ruttinger, regional director of the charter school network Imagine Schools, which has 13 charters in Arizona, argued that all grades should be suspended until the revisions are final.

“Charter schools especially are affected by current grades,” she told the board.

Eileen Sigmund, president of the Arizona Charter Schools Association, told board members that beyond penalizing high-performing schools, the current formula also bars many smaller charter schools from receiving grades, which means they can’t be considered for additional “performance funding” for schools with A grades.

Though they make up roughly 30 percent of schools in the state, charters comprise nearly 60 percent of the schools listed as under review either because of formal appeals or their unusual grade configuration.

On the opposite end of the spectrum, critics noted that the student-growth formula doesn’t go far enough to equalize the impact of socioeconomic status on school grades.

Board member Patricia Welborn noted that under the current formula, only 5 percent of high-poverty schools received an A, while roughly 25 percent received Ds or Fs. By contrast, half of low-poverty schools received A’s, 90 percent received A’s or B’s, and none received an F or a D.

“I’m very concerned that one of the fundamental rules that we intended not to happen, has happened. And I would like us to look at this issue,” she said.

Contact reporter Hank Stephenson at hstephenson@tucson.com or 573-4279. On Twitter: @hankdeanlight