Hallways at Bibbs were lined with posters of sample answer sheets for the state assessment tests and with efforts to redefine the dreaded ''F'' label: ''We are Fueled, Focused and Fighting.'' At Dixon, there is a trophy case of prizes -- Pokemon toys, a Sony PlayStation, a television -- for those who score best on the tests.

Inside every classroom, the mission is clear.

In Vickie Ward's fifth-grade class, there was an orange F.C.A.T. math workbook on every desk as Ms. Ward drilled the students on writing multidigit numbers in standard form -- numerals -- and word form. Fifth-grade math scores count toward the school grade.

Rosa Dean's fourth graders were practicing a reading comprehension exercise; their reading scores help determine the school's rating.

''You do the process of elimination,'' advised Mrs. Dean, sounding like the test-preparation gurus who coach teenagers for the College Boards. ''You have four choices; try to get it down to two choices.''

Teachers at Bibbs and Dixon, and the parents who spurned the vouchers, blame the F's largely on demographics: many of their families are headed by single mothers or grandmothers on welfare with little education; kindergartners arrive never having picked up a book, not knowing the alphabet.

''I have a bicycle, and the man next door has a Cadillac,'' said Georgia Smith, a kindergarten teacher at Bibbs. ''If you're going to compare the distance I can travel with the man who has a Cadillac, well, let me swap vehicles with that man, and then see how far I can travel.''

Indeed, across Florida, no school where less than 10 percent of the students qualify for free lunch scored below a C, and no school where more than 80 percent of the students qualify scored above a C.

Many Florida educators want the results to take account of socioeconomics, or focus on a school's improvement from year to year, rather than judging all schools on the same criteria.

Tom Gallagher, the state's education commissioner and the architect of the school-grading plan along with the governor, said improvement would help dictate school grades as soon as the assessment tests are old enough to track annual progress. But ''our expectations are the same for a first grader in Coral Gables as it is for Bibbs or Dixon,'' he insisted. As for whether test preparation has squeezed out enrichment programs and even basics like science, Mr. Gallagher is not worried: Nobody can pass the test, he noted, without reading its directions.

''You can't operate in our society if you can't read, write and do math,'' he said. ''You can operate in our society if you haven't been on a field trip, if you haven't had any art this year, if you haven't been to gym, and if you haven't had any science.''

Though parochial students do not take the tests, those using vouchers must. So there were no signs of the test -- no posters in the hallways, no mention of multiple-choice bubble techniques -- at Little Flower, one of the five private schools, four of them Catholic, where former Bibbs and Dixon students have enrolled.

In classrooms arrayed around a central courtyard with a fountain, fifth graders were writing persuasive letters, while first graders put on a puppet show.

''Last year, it was nothing but work sheets,'' said Patricia White, whose daughter, Katrina English, took a voucher. ''Now, homework every night, books, essays to write. We just finished a report with poster board and such -- we didn't even leave the house last Saturday!''

Teachers say they have tweaked the curriculum -- cutting spelling tests to 10 words a week from 20 for one boy -- but that the acculturation process was not much different than with other public-school transfers.

Many voucher families had always wanted to send their children to private school but could not afford it; some were just fed up with what they saw as behavior problems and low expectations at Bibbs and Dixon.

Andy Cameron, whose son, Ray, was repeating fourth grade this year at St. Michael's, called Dixon ''a giant sewer'' where ''the academic atmosphere was nonexistent.''

Ms. White said she volunteered in Katrina's class every day last year, and saw third graders still struggling to identify letters; even if vouchers are ruled illegal, she will keep Katrina in Catholic school.

''I got cable; it'll go,'' Ms. White said. ''The telephone? That's a luxury. I will get a night job. I'll do what I have to do. She's getting a better education.''

In this very enthusiasm over the children's progress lies a potential pitfall. Whether vouchers are targeted by income, as in Milwaukee or Cleveland, or by school performance, as here in Florida, they are typically seized by families with relatively more money and better educational backgrounds; the most disenfranchised of the disadvantaged groups stay behind, only making the educational challenge steeper.

As Bibbs and Dixon struggle to get off the ''F'' list, principals and teachers are working overtime, and children are focused as they study in small groups, aided by an influx of volunteers serving as mentors.

Evaluating their effectiveness is tricky. In the writing laboratory at Bibbs, fourth graders cheerily chant a rhyme about adverbs; but they cannot name any. They enthusiastically sing a song diagramming sentences, but when asked to define a ''predicate,'' one of the items they have just identified, the children are at a loss.

At Dixon, a simple sign suggests the complexity of the challenge: ''Teach half as much, twice as well.''

Correction: March 18, 2000, Saturday

A front-page article on Tuesday about a school voucher program in Florida misidentified the school where students were unable to identify a predicate after singing a song that referred to one. It was A. A. Dixon Elementary in Pensacola, not Spencer Bibbs.