Following a trend, Florida's school grades showed strong gains in the third year after the state changed its grading formula and the standardized tests that students take every year.Statewide, the number of schools earning A's and B's jumped 20 percent, to 1,834, while those receiving F's dropped 61 percent, to 43. Among schools that earned an F a year ago, 79 percent improved by at least one letter grade, according to results announced Wednesday.The news came against a backdrop of a recently closed legislative session that saw lawmakers limit turnaround options for the state's lowest-performing schools and made it easier to shut them down if they continue to score poorly. The Florida Department of Education still is sorting out the details of the new law.Some of the schools most affected by the law made huge jumps this year.ALL EDUCATION, ALL THE TIME:The Gradebook blogWANT TO KNOW YOUR SCHOOL'S GRADE? Click here.In Pinellas County, for instance, Melrose Elementary — Florida's lowest-performing elementary school three years ago — brought itself up to a C from an F. Pasco County's two F-rated schools, Hudson and Calusa elementary schools, likewise improved to C.Miami-Dade County, which had 16 F schools two years ago, had none this year.The arrival of school grades, which usually are reported in early to mid July, took many school officials by surprise. But they highlighted what many educators have come to expect from the state's test-based accountability system, which is in its second decade. After a major change to the system, performance dips and then recovers as teachers and students become accustomed to the differences."We're not in the middle of a change in tests. They haven't changed the grading formula. This is the third or fourth year of consistent focus on the same thing," said Pasco County assistant superintendent Vanessa Hilton.That consistency has allowed schools to delve deeper into their efforts of aligning their teaching to state standards, and providing "rigorous learning opportunities" for the students. It's not teaching to the test, Hilton said, but it is yielding positive results.At Bear Creek Elementary in St. Petersburg, Willette Houston, a brand-new principal, came up with a bold motto at the start of the school year: "On our way to an A!"The school, which has 100 percent poverty and 61 percent minority students, had never earned an A before. But Houston put the motto on staff T-shirts and in the school newsletter. On Wednesday morning, she learned that the school had indeed jumped to an A from a C. She was stunned."I don't even know how I feel right now," she said. "It's been a long journey."The state's grading system often faces criticism as a measure of little more than socioeconomics — because schools with more affluent students typically perform better — but education commissioner Pam Stewart said Wednesday that it was putting a focus on all schools and their needs. The grading formula gives schools credit for both how many students score on grade level and how many students made learning gains in core curriculum areas of math, language arts and science.At Melrose, for instance, overall achievement in mathematics was low, with 33 percent of students on grade level or better. But there were huge gains, with 61 percent of students improving. Of the bottom quarter of students, 73 percent made gains.One way the state keeps tabs on low-peforming elementary schools is with a list of the bottom 300, based on language arts scores. Those schools are required by the state to offer an extra hour of reading instruction.No district in Florida had more schools on the list than Hillsborough County.Among them, Potter Elementary School in East Tampa received an F for the fifth straight year, despite superintendent Jeff Eakins' promises to the state Board of Education last year that he would make improvement there his top priority. Booker T. Washington Elementary, which along with Potter had been designated as an "Elevate" school and slated for extra resources, also remained an F.Eakins said that at both Washington and Potter, the principals are just now finishing their first year at their schools. "It takes a year to create that right foundation," he said. "Year one is always about creating the right conditions in the schools."At a news conference in Tampa, there were flowers and balloons for the principals of Miles, Dunbar and Shaw elementary schools, which all improved to a C from an F this year.Eakins celebrated that there are now 51 traditional A schools, up from 41, and three F schools, down from seven in 2016 and 18 in 2015. Early in his tenure, he announced plans to dramatically improve the seven Elevate schools, which all serve high-poverty communities. Miles, one of the improved schools, was in that group.In Pinellas County, the number of A or B schools went up, and several schools improved by two letter grades. In its Transformation Zone, where low-performing schools get extra resources, three of the eight schools jumped two letter grades, including High Point Elementary in Clearwater, and Campbell Park Elementary and Melrose, both in St. Petersburg. The other five zone schools earned D's or F's.At High Point, which rose to a B from a D, the new principal, Michael Feeney, said he felt a "sense of relief and pride" for his teachers."We were doing a little bit of dancing today," he said.Both Campbell Park and Melrose earned C's after being ranked F's. Melrose had been an F school for six years.Pasco County saw all but four of its schools, including charters, either maintain or improve their grades. Nineteen received A's, 22 got B's and 37 earned C's.Some of Pasco's most struggling schools made giant strides.In addition to Lacoochee, Hudson and Calusa, four other elementary schools — Pine View, Quail Hollow, Gulf Trace and Moon Lake elementary — rose two letter grades. Several schools on the state's accountability watch list, including Pasco and Gulf Highlands elementary, and Gulf and Hudson middle, also bettered their marks."We're really happy the work our teachers did yielded results," Hudson Middle principal Joe Musselman said.Just one Pasco school, West Zephyrhills Elementary, received a D, its second in a row. In Hernando County, all schools maintained or improved their grade from last year, with the exception of John D. Floyd Elementary, which dropped from a B to a C. Superintendent Lori Romano said she was pleased to see the district's overall score bump up 23 percentage points, putting it closer to the top grade. Hernando earned a B for third straight year, as did all of the Tampa Bay area districts.Both Spring Hill Elementary and Chocachatti Elementary rose from a B to an A. Others making gains were Brooksville Elementary, Springstead High, Parrott Middle, Pine Grove Elementary and Nature Coast Technical High. Moton Elementary again fell on the list of the state's lowest-performing schools, earning a D for the second year in a row.Even at schools with improvement, educators had no plans to sit still. Lacoochee Elementary principal Latoya Jordan, whose school rose from an F two years ago to its first B since 2008, said celebrations have their place, but they can't last long."I compare the school grade to a basketball game," Jordan said. "After you make a spectacular basket, you can't just stand down at the one goal and marvel at the shot. It's a long game."Staff writers Megan Reeves and Marlene Sokol contributed to this story. Contact Jeffrey S. Solochek at (813) 909-4614 or [email protected] Follow @jeffsolochek.