NEW YORK - Adolescence can die young.

For Tafazzul, a teen-age Bangladeshi immigrant who had arrived in this country without his parents, the moment came when his older brother was blown up three years ago by a trash-can bomb on Manhattan's Lower East Side.

Left with $400 in monthly rent, to meet, two younger brothers to feed and no adults looking after them, Tafazzul, then 16, quit high school to work 15-hour days as a shop clerk.

"I wish I had my parents here when I was in high school," Tafazzul said, his eyes casting downward. "They don't have to do anything for you. But it's a nice feeling to know that when you are tired, you will have their shoulders to lie on, and that's enough."

Many on their own

Tafazzul, who would give only his first name, is among the thousands of Bangladeshi students who have gone through New York City's public school system in the last decade. The majority of them have legally immigrated to America with their parents and are being supported by them.

But dozens of them, like Tafazzul, are living in city tenement buildings on their own, leaving their parents behind in Bangladesh so they could flee a country ravaged by relentless poverty, natural disasters and political instability.

To support themselves, they deliver pizzas, cut flower stems at corner grocery stores, sell souvenirs on sidewalks and wait tables at restaurants after school and on weekends.

Often, four or five of these boys share a studio apartment in the tenements on the Lower East Side, in Harlem or in Jackson Heights, Queens, each contributing his share of the rent. For those who manage to stay in school, homework comes only after the end of late-night shifts, if at all.

Hardship, however, is hardly reserved for those immigrants without parents. Hundreds of Bangladeshi students with parents also work long hours after school to help support their families.

Some send as much as $100 every month - enough to feed a family of three there for a month - to relatives in Bangladesh, said their school guidance counselors, a couple of whom are Bangladeshi immigrants themselves.

Downside for schools

But that immigrant energy sometimes has a downside for schools that enroll the Bangladeshi students. The confluence of poverty, lack of early schooling and language barriers, combined with the need to work long hours, frequently drives many of these Bangladeshi youths out of school. Nine of 10 at Seward Park High School on the Lower East Side, for instance, drop out, said a Bangladeshi teacher there.

"It's very hard for them to keep up," said Meenakshi Datta, a guidance counselor for the Bangladeshi students at Seward Park. "They talk different. They don't have the academic preparation to get ahead, and their families need them to work."

Datta, who came from Bangladesh seven years ago, is familiar with how these children made their way to America. Most, she said, came legally with their families, who have succeeded in getting visas through a lottery by the Immigration and Naturalization Service that aims at improving diversity among America's immigrants. But many of the boys - and they are virtually all boys - who live here by themselves frequently entered the U.S. ports illegally.

"Sometimes, some boys' parents would pay families with legal papers to take their sons to the U.S.," Datta said.

In other cases, she said, some families would sell all their possessions, including their land, to bribe a Bangladeshi staff member in the U.S. Embassy to procure for their sons visitors' visas, which are hard to get. Once here, the Bangladeshi boys would overstay their visas and become illegal immigrants.

But the road toward some measure of economic success is hardly the same legendary road traveled by other immigrants, even for those with their parents here. For one thing, the young Bangladeshi immigrants are often behind their American peers in academic preparation.

"In Bangladesh, as soon as kids turn 11 or 12, many parents send them to work in factories or drive rickshaws," said Shaon Ahmed, now 23, a Bangladeshi native who attended Seward Park High. "They don't believe in school."

70 percent illiteracy

Illiteracy in Bangladesh hovers at close to 70 percent, according to data from the United Nations. But even for families that put a premium on education, formal schooling for their children can often be interrupted by typhoons, hurricanes and, for girls, traditional responsibilities such as tending to ailing relatives.

"Some Bangladeshi kids come to this country at 15, 16, and they are placed in 10th or 11th grade because of their age," said Mohammed Abul Kalam Azad, a Bengali teacher at Long Island City High School in Queens. "But they really only have had a fifth- or sixth-grade education, and they are not ready for 10th or 11th grade."

There are a handful of Bangladeshi teachers in the city's public schools, like Seward Park High and Long Island City High, teaching Bengali as a foreign language.

Many of the city's 3,500 Bangladeshi students take their classes to fulfill their foreign language requirement. Invariably, the service of these teachers are in great demand.

In most cases, the new Bangladeshi students take a few periods of English as a second language a day but sit in the regular classes for other subjects, since subject classes such as history or global studies are not offered in Bengali by the New York school system.

Bangladeshis are among the fastest growing minority in the city; their number quadrupled to close to 20,000 from 1990, according to the 2000 census.

Ahmed was one of the few Bangladeshi teen-agers who have graduated from high school while living alone.

"Every day, I would be in classes and keep talking to my classmates sitting nearby," recalled Ahmed, who graduated from Seward Park three years ago. "That was the only way to keep myself awake. I always had to work the previous night."

Now a junior at Baruch College and a part-time cabdriver, Ahmed said he owed his success to his own determination, stamina and the companionship of a Chinese immigrant girl, whom he eventually married. Both sold souvenirs at a gift shop in Chinatown for $2.75 an hour.

'We were abused'

"I know we were abused," he said of the wages, "but the owner was the only person willing to pay us off the books. And trust me, there are a lot of people around who are willing to work for that price."

Such freedom is hardly accorded to Bangladeshi girls. Once they have been detected dating, some have been pulled out of schools by their families and sent back to Bangladesh to marry a partner chosen by their families.

Many of the Bangladeshi children are poignantly aware of the difference between their situation and that of American peers who may be busy worrying about choosing the right sneakers and filling out resumes to impress college admissions officers.

Abdul Munaf, 16, a student at Seward Park, waits tables to help support his father in New York, who is too sick to work. His sister Zaheda Begum, 17, goes to Seward Park and works after school, too.

Abdul said he wished that he might be able to play soccer with friends after school instead of rushing to the Indian restaurant.

Ahmed would have liked to have joined a school band, and he said that he always stayed away from bars, fearing being swept up in a brawl.

"I really wanted to be just like the other kids, you know," Ahmed said.