Last in an occasional series about the grades that provide the building blocks of a child's education.

The sixth-grade boy burst into the school's main office with brown hair flying, school binder clutched to his chest, eyes watery from reluctantly spilled tears. In an emotional burst, he told Assistant Principal Mary Beth Pelosky that a teacher "misheard me and thought I said a bad word which I didn't and sent me here."

Moments before, he had been happily writing an assignment about why sixth grade had been great. Now he was counting backward to reclaim control of his emotions -- and in no time, he would be back in class, recovered, as if nothing had happened.

"That's sixth grade," said Pelosky, of Swanson Middle School in Arlington. "The students are wonderful, creative and curious, but they are still kids, trying to grow up, and that makes them very, very emotional."

Up, down, all around: It's the state of sixth-graders -- and sixth grade, kids and adults say. It is a weird year, full of physical, emotional, social and logistical transitions that schools meet with wildly varying levels of success.

Parents see their children, on the edge of adolescence, often like strangers, exuberant one minute, crushingly sad the next. Kids say it is a time when things are far more different than ever. "Everybody is going crazy," said Rebecca Lesher, 12, a sixth-grader at Mann Elementary School in the District.

Translation: They become moody, rebellious, hormone-driven. Kids are friends one minute, enemies the next. More students talk back to their teachers than before, and peers matter more than ever. Kids who barely uttered a word in fifth grade are the class clowns in sixth. And everyone is just "so awkward," recalls Julia Penn, 18, who just graduated from Montgomery Blair High School in Montgomery County and remembers sixth grade as the "worst."

It's not just students and parents who find sixth grade so baffling: Educators can't agree on where sixth-graders belong. Consequently, they can be found as the biggest and toughest kids in elementary schools with grades K-6, or near the top in K-8 schools, or at the bottom of 6-8 middle schools, or near the bottom of 5-8 schools.

There also are scores of schools where sixth is the only grade and the school is seen "as the first step in the big, bad world," said Rod Coykendall, principal of the Derby (Kan.) Sixth Grade Center.

"The way we have it set up is certainly challenging for the kids," said Mary Pat McCartney, counselor at the K-5 Bristow Run Elementary School in Prince William County.

What to do with emerging adolescents has been the subject of a decades-old debate that shows no sign of abating. Early 20th-century American schools placed sixth grade squarely in elementary school, which ended in eighth grade. That started to change after the end of World War I when more schools began ending elementary schools with sixth grade.

In the latter part of the century, millions of sixth-graders were moved to middle schools, which most often had grades 6 through 8. Some changed their academic and social programs and became successful; others, especially in urban areas, became crowded and did nothing to adapt to student needs. The schools developed reputations as a weak link, with out-of-field teachers generally teaching a larger percentage of students in the middle grades (grades 5 through 9) than in high school, according to the U.S. Department of Education.

The pendulum seems to be swinging again. Now, in about a dozen American cities -- including Baltimore and New York -- administrators are trying to eliminate middle schools and reverting to K-8 schools, said Prof. Paul George, an expert on middle schools at the University of Florida. (In the District, Superintendent Clifford B. Janey has said he likes the K-8 model and will start to review the organization of grades next year.) George, however, said he is skeptical of the trend.

"There are so many unknowns, and I'm afraid in these dozen school districts, where admittedly good middle school programs are not commonly found, that they are going to do K-8 the same way they do 6-8, and that is with ignorance," he said.

Still, superintendents such as Paul Vallas in Philadelphia are proceeding with the transformation, saying that middle-level students will do better in a smaller, more nurturing environment and that he is pumping in enough resources to make the transition effective.

Vallas, who is guiding a reduction of 46 middle schools to eight by 2008, said that studies in Philadelphia show that sixth-graders in the elementary environment perform better on standardized tests than sixth-graders in middle schools. He is also being driven by new research (by the nonprofit Philadelphia Education Fund in conjunction with Johns Hopkins University) showing that almost half of high school dropouts can be identified as early as the sixth grade, based on four variables: low attendance, poor behavior, failing math and failing English grades.

"The sixth grade, now that's when the physical, emotional and psychological changes really accelerate," he said. "And to move them from the quasi-tranquillity of that K-5 school and suddenly place them in a middle school building, which normally, in urban areas, has 800 to 1,000 kids from eight or nine neighborhoods -- that's an absolute disaster."

There are, predictably, partisans of other grade configurations.

At Mann Elementary, students and teachers say they like the K-6 model, allowing sixth-graders -- who are mostly 11 or 12 years old, the space to test their wings in a comfortable environment. There they see a number of teachers but spend most of their time with one.

"They are aspiring to be teenagers, but they are not there yet," said teacher Terri Kominers. "They still have their innocence, and there's nothing wrong with trying to maintain that."

Bogdan Loukanov, 11, agreed. "The more you can put off the change, the better."

But over at Swanson, Sandy Hart, 12, said he is glad to be out of elementary school. "I really like the freedom" of middle school, he said in science class as he was cutting cardboard to make a model of an energy-efficient kitchen.

Swanson Principal Chrystal Forrester said a high-performing middle school with grades 6-8 "is a good bridge" between elementary and high school, and offers students an appropriate transition.

Her sixth-grade program is geared to helping students adjust to the demands of a new, larger school, where the kids have gone quickly from being the oldest to the smallest and youngest.

Sixth-graders attend classes together in one wing of the school, changing classes every period, with new teachers. There are more choices -- clubs, sports, after-school activities -- and students are expected to operate more independently. Ultimately, she said, sixth grade is about growing up -- for the kids and their parents.

"The hardest thing for parents is that sometimes we have to let our children fail, make a mistake in a safe environment," she said. "So hopefully in a less safe situation, they will make the right decision."

At right, Dan Reilly elicits responses to his prodding questions of sixth-graders in his reading class at Swanson, in Arlington. Educators disagree on whether sixth-graders should be the oldest and biggest students in a kindergarten through sixth-grade school or the youngest in a middle school that starts with sixth-graders.Psst! Will Ferguson, left, passes a note to Matt Wetmore. Sixth-graders are "wonderful, creative and curious, but they are still kids, trying to grow up," says Assistant Principal Mary Beth Pelosky at Swanson Middle School.