JACKSONVILLE, Fla. -

The number of top-rated schools in Florida is falling sharply and the number of failing schools more than doubled over the last year while the number of "A" schools dramatically declined nearly 39 percent -- from 1,242 schools in 2012 to 760 in 2013.

The Department of Education had warned superintendents that the grades were expected to go down because of higher standards implemented in state standard this year, and the drop was significant.

In Duval County, three middle schools, seven elementarily and one charter school received F grades.  Another 27 middle and elementary schools in Duval County were graded D.

A middle school and a charter school in Columbia County schools received F grades, as did an elementary school in Putnam County.

School grades table High school grades come out later because the graduation rate and other factors are included in those evaluations.

SPREADSHEET: Grades for NE Florida schools

The number of F-rated schools could have been much higher. Earlier this month, the State Board of Education voted by a 4-3 margin to tweak the formula that allowed as many as 150 schools to avoid getting an F grade.

Duval County School Superintendent Nikolai Vitti said the declines are largely due to the raising the state's grading system, not by any deterioration in the quality of schools.

"It is counterintuitive to believe that grade level performance, the purest determinate of student achievement, can improve across multiple grades and subject areas, yet school grades decline," Vitti said in a statement released Friday. "The number of F schools in the state increased by over 260 percent since last year. It is not mathematically possible that in only one year over 260 percent more schools could be considered failing than the year before.  We must demand that we have a consistent way to measure academic performance in Florida or public confidence in the accountability system will continue to erode. I believe that we certainly have room to improve in Duval County, but I am looking forward to the day when we can compare "apples to apples" to measure performance."

The decision to change the grading standards was done over the protest of some officials who said the move would confuse parents and mask the true performance of many schools.

The Florida Education Association, the main state teachers union, responded to the report cards by blasting the grading system Friday.

"The constantly changing measures the Florida DOE uses in grading schools renders them meaningless as a comparison of school progress," FEA President Andy Ford said. " ... This system is flawed and does not reflect rising student achievement and the dedicated and caring efforts by our public school teachers and other school employees to provide our children with a high quality education."

Education Commissioner Tony Bennett said he expected the "volatility" in grades to continue over the next three to five years.

"This is exactly why I made the recommendations I made to the board," he said.

School district grades for the 2012-2013 year were also released Friday.  Duval County retained its C grade and St. Johns retained its A. But Clay, Flagler and Nassau counties' grade dropped to a B, and Putnam County dropped from a C to a D.

Within the bleak report, there are pockets of good news.  Among the 32 schools in Duval County to receive an A this year is Mayport Elementary School, which brought its grade up from a D last year.

Kimberly Bloor Duffield, an academic coach at the school, says efforts to improve the school are paying off.

"We had to come together as a faculty, and we changed a lot of things," she said. "Teachers had to let go of some old practices and bring in some new things."

Superintendent Vitti says what worked at Mayport is

"What works commonly in a F school is the same type of work that is done at an A school. Our children need to be exposed to the arts and music, to develop as a child," Vitti said. "We have to get away from teaching to the test. We have to teach our students how to think on their feet."

That is something parents and teachers at Mayport elementary say they have been doing, and it's paying off.

"I am very proud," said Penny McDonald, PTA president at the school. "I really enjoy this school. My son has succeeded. I could not ask for a better school for him to be in."