A new method of calculating graduation rates reveals two things about Georgia high school students: More are dropping out than had been previously counted and a sizable number are taking five or six years to earn a diploma.

Georgia’s 2011 graduation rate plummeted 13 percentage points under the state’s new formula, to 67.4 percent from 80.9 percent. Before the new calculation, which was released last week, school districts often masked dropouts as transfers; they could also count students as graduates no matter how long it took them to finish.

An Atlanta Journal-Constitution analysis of the new graduation data shows seven metro Atlanta districts lost even more ground than did the state as a whole. In addition, 57 Georgia schools, 20 of them in metro Atlanta, failed to graduate even half of their students.

With academic standards increasing, state Schools Superintendent John Barge warned that graduation rates could look even worse for 2012.

“I’m thinking they might,” Barge said. “I’m not sure how much lower.”

State analysts have not done a deep dive into the data but say they are convinced that part of the decline in the graduation rate results from more students taking longer to graduate. Probably 5 percent to 10 percent of high school seniors now require a fifth or even sixth year to finish, Barge said.

What’s happening in Georgia — including an undercount of some dropouts — is occurring in other states as they embrace the new grad rate formula.

“A lot of states were using [the same formula as Georgia was] and are bracing themselves for drops in their graduation rates,”said Tara Tucci, senior research and policy associate at the Alliance for Excellence in Education.

The disparity was worrisome to some parents.

At College Park’s Banneker High, among Fulton County’s lowest performers, the graduation rate dropped sharply, from the 67.3 percent shown on the school’s accountability report for last year to about 42 percent under the new criteria.

“I am very concerned, I have a sophomore there,” said Alice McNabb. “I would like for the school to find more ways of reaching kids. Every child doesn’t learn in the same way.’’

Georgia’s graduation rates have been held up in recent years as an emblem of school improvement. Gov. Sonny Perdue trumpeted news in 2010 that Georgia had finally surpassed the 80 percent benchmark.

The rate is considered a key barometer of educational progress — so much so that schools use their graduation rates to prove they made Adequate Yearly Progress, the benchmark of success under the federal No Child Left Behind Act. Businesses eye the rates when choosing where to locate. Even as the state escapes the mandates of No Child Left Behind, graduation rates will still be used to measure success in Georgia. Precisely how much weight will be given is still to be determined.

More students drop out

That Georgia has a dropout problem is no surprise to two Clayton County sisters who left Jonesboro High School within the past two years. Dyane Humphrey said she couldn’t stand being bullied. Lonnie Humphrey departed after falling in with the wrong crowd. The sisters say the school failed them.

“You have counselors who can’t really help you in situations,” Dyane Humphrey said.

The sisters say they’ve had better luck since leaving. They earned GEDs and are heading to Atlanta Area Tech in the fall. Dyane plans to major in business and hopes to own a funeral home one day, while Lonnie is interested in the culinary arts.

In many school districts, there’s a good chance the Humphreys would have been counted as transfer students rather than dropouts, a move by which schools inflate their graduation rates.

In April 2010, the U.S. Department of Education issued a rebuke to state education officials and Clayton County for under-counting dropouts. An AJC investigation unearthed problems in Atlanta Public Schools, determining that many students were marked as transfers despite no evidence to show they had enrolled in another school.

The new formula hones in on dropouts. It requires schools to verify student transfers, ensuring that those students are enrolled in another school. Otherwise, the students are counted as dropouts. In the past, no such verification was required.

In addition, a new multimillion-dollar data system that maintains a file on every schoolchild means that districts and the state will be better able to track students. That is expected to improve the accuracy of graduation rates.

The new calculations released last week count students who made it from ninth grade to graduation in four years. The new formula, which was mandated in 2008, is “the gold standard,” said Jeff Gagne, director of education policies for the Southern Regional Education Board.

College students taking longer than four years to graduate is such a well-established trend that universities calculate a six-year graduation rate. The phenomenon of “super seniors” is newer to high schools, but Superintendent Barge’s estimates suggest that 5 percent to 10 percent — thousands of students across the state — are now taking longer than four years to finish school.

Anne Hyslop of the Washington-based Education Sector said this can put a student behind in college and in entering workplace.

“The more detours you take along the way, the more chances that you may not stick with it. That is a danger,” Hyslop said.

Still, school officials in Gwinnett County say the diploma, and not the number of years it takes to get one, is the most important thing.

“We have a lot of kids who have to have more time,” said Jason Lane, principal at Duluth High School.

The pressure is more intense with a move to require 23 credits to graduate, Lane said, noting that a full-day schedule for four straight years delivers 24 credits.

“There’s not room for mistakes,” Lane said.

The graduation rate at Duluth High fell to 70.5 percent, down 15 percentage points.

The drops between the old rates and new ones were particularly wide in alternative schools, geared toward nontraditional students.

At Independent Alternative School in Fulton County, the graduation rate fell from 68 percent under the old formula to 38.5 under the new one. Principal Tabitha Taylor said the decline didn’t surprise her.

“It’s our objective to help them graduate, even if it’s later,” Taylor said.

In Georgia, students can attend school for free until age 20. At age 21 they must pay to remain in public high school.

Some educators are still shooting to see their students graduate in four years.

“Are the expectations a little higher? You bet they are.” said Keith Chaney, principal at Gwinnett’s Mountain View High School. “The more rigorous we are with kids the better they are when they leave us. I don’t think it’s harder to graduate. It is challenging and I think that’s a good thing.”

Chaney said principals in Gwinnett, the state’s largest school district, last year began working together on issues surrounding graduation rates. One strategy is reviewing students’ records stretching back to third grade to see which are at risk of dropping out.

For some districts, the drop in the graduation rate was far less dramatic than it was in others, giving parents confidence in their school’s strength.

Chattahoochee High School in north Fulton County, for example, saw its graduation rate dip about 6 percent, to 90 percent, still well above the average for the state and many other metro Atlanta high schools.

“It’s a great school,” said Margaret Cohen, the mother of a senior who will be attending the University of Georgia in the fall.

-- Staff database specialist Kelly Guckian and staff writers Tammy Joyner, Ty Tagami and D. Aileen Dodd contributed to this article.