ENSENADA, Mexico - Ryan Fraidenburgh was 14 when he was brought here shackled, kicking and screaming.

Two men carrying handcuffs and leg irons came for him at his mother's home in Sacramento, Calif., shoved him into a van and bound him hand and foot. They drove him 12 hours south, over the Mexican border, into a high-walled compound near here called Casa by the Sea.

"It was nighttime," Ryan recalled. "I look around and I see kids sleeping on cement. I was really, really scared. The big honcho, Mauricio, said, `You don't speak English here.' I didn't know how to speak Spanish."

Ryan quickly learned the rules: stay silent, be compliant, don't look up, don't look out the window, don't speak unless spoken to. The punishments for breaking the rules included solitary confinement, lying on the floor in a small room, nose to the ground, often for days on end.

Ryan was not a criminal. He was only skipping school, his parents said in telephone interviews. But in August 2000, they said, in the middle of a bitter divorce and custody battle, they decided to send him away to Casa by the Sea, which calls itself a "specialty boarding school" for behavior modification.

Like hundreds of other parents, the Fraidenburghs made their choice largely on the basis of a glossy brochure and a call to a toll-free number in Utah. They came to regret their choice.

The idea of sending a child to such a program in Mexico was unheard of a decade ago. But in the United States, behavior-modification programs and boarding schools for troubled youths have faced increasing legal and licensing challenges over the past few years.

More and more are moving abroad - some to Mexico, Central America or the Caribbean - where they operate largely under the regulation radar and where some employ minimum-wage custodians more than teachers or therapists, say government officials, education consultants and clinical psychologists.

The behavior-modification business is booming at Casa by the Sea, on Mexico's Pacific Coast, the largest of 11 affiliated programs with roughly 2,200 youths, about half of them in Mexico, Costa Rica and Jamaica. The programs are run by a small group of businessmen based in St. George, Utah, under the banner of the World Wide Association of Specialty Programs and Schools, or Wwasps, and Teen Help, the programs' main marketing arm.

Over the past seven years, local governments and State Department officials have investigated Wwasps-affiliated programs in Mexico, the Czech Republic and Samoa on charges of physical abuse and immigration violations. The Mexican program, in Cancún, and the Czech program closed, and their owners left those countries saying they feared unjust charges. The Samoan program cut its affiliation with Wwasps.

Ken Kay, the president of Wwasps, would not allow a reporter to visit Casa by the Sea; Dace Goulding, the program's director, declined to answer any questions. But Mr. Kay, responding to inquiries in writing from his office in Utah, said no charge of abuse had ever been proven against any of the programs in any court.

"We are about getting families back together," he said in a written statement. "We are not for everyone, and there are very few but vociferous critics of not just us but any youth intervention." He described many of the program's critics as parents who feel they have been "manipulated, brainwashed or duped" or who are battling through divorce and taking their anger out "by making us look terrible."

In telephone interviews, eight teenagers who were formerly in Casa by the Sea described a system in which the youths try to ascend six "levels" through a system of rewards and punishments, including being sent to "R and R," a small, bare isolation room, often for days on end. Discipline, not education, was the rule, they said.

For Laura Hamel, 17, of Vienna, Va., who counts herself as a success story, it was a slow two-year ascent to graduation in March. She said she was demoted from Level 3 back to Level 1 after giving a weeping, lonely friend a hug and a kiss on the cheek at Thanksgiving. Affection of that kind is forbidden.

A youth who rises to Levels 4, 5 and 6 can become a "junior staff member" and "participate in the discipline process" against lower-level youths, Casa's contract with parents says.