It seemed to Virgil de Voldere that with each passing year his son attended the P.S. 84 Lillian Weber School, it only became more popular.
On the tours he organized for prospective parents, numbers swelled from a few dozen to several hundred. Families who lived in other districts began to apply, preferring the school on 92nd Street between Columbus Avenue and Central Park West to their zoned option.
A school that middle class parents once kept their distance from was now attracting them with French and Spanish dual-language classes, after-school programs and an increasingly active Parent Teacher Association.
"There was a renaissance," Mr. de Voldere said. And then came the city Education Department's report card on the school's progress from 2010 to 2011: A grade of "F."
Described by the city as a public information tool, the annual A-through-F grading system has left some parents mystified since its introduction in 2007. And every year there are a few cases like P.S. 84's — a school parents insist is on the up, and city data analysts' couldn't agree less.
Confusion set in, and even after the grade was explained to them, many parents barely understood its origin. They wondered how they would win over new families who would comb through the city's reports and discover the big, red F.
"I just thought how can this be?" said Talcott Camp, the mother of two P.S. 84 students. "Is there room for improvement? Yes. But is the school overall a failing school? It’s absurd."
The city bases grades for elementary and middle schools largely on one year's movement in test scores -- progress counts for 60 percent, performance for 25 percent -- and parent and teachers' responses on an annual survey are worth 15 percent. It compares schools' scores with those of peer schools, using a formula to determine which schools have similar types of students.
As principal Robin Sundick, 59, understands it, the comparison to peer schools explains much of her school's grade. P.S. 84's student body is undergoing a radical change, she said. While her third through fifth graders are predominantly black and Latino and many meet the city's measure of poverty, their younger, untested schoolmates are increasingly white and middle class.
Last school year, there were 123 white students in a school of 518. In 2004, when Ms. Sundick became principal, 32 students out of 570 were white.
Now that P.S. 84 has fewer minority and low-income students, the city has altered the group of schools to which it is compared. But the principal and parents say they are being unfairly judged against schools where students who take the test are better off than their own.
"The testing grades don't match the statistics that you see in the peer index," Ms. Sundick said. "On average, 73 percent of her students are black or Hispanic and about 54 percent are eligible for free lunch. Among the students in the tested grades, those percentages are higher," she said.
"That's where the disconnect lies," she said.
But there's also the hard truth of the school's test scores, which show less than half of students testing as proficient on the state math and English exams. Those scores are an increase over its performance in 2010, but they remain below the citywide average.
And the school didn't score any bonus points with the city, which awards extra credit to schools that excel with special education students, English language learners, and black and Latino boys. According to city Education Department officials, P.S. 84 hasn't done that.
And while parents who filled out the city's survey raved about the school, its teachers had a mixed response.
"While the school has a longstanding dual language program and a committed staff and parent community, student achievement -- especially for its most vulnerable students -- is lagging," said Chancellor Dennis M. Walcott in a statement. "We need the school community to pull together around the common goal of improving the quality of classroom instruction instead of debating the mechanics of the progress report."
Unable to reconcile the failing grade with the visible signs of improvement, P.S. 84's PTA responded last week by distributing individually wrapped roses to the school's staff. Pinned on the flowers was a note.
“Dear PS84 Teachers and Staff,” it began, “In light of the recent city progress reports, the PTA Executive Board and families at PS84 want our teachers, staff, and administrators to know that we find this grade label to be arbitrary and inaccurate.”