Police officers and substance abuse counselors in suburban communities south of Boston said hotels are increasingly popular destinations for celebrating teenagers. Some adults rent high school students a room knowing that alcohol will be served so that teenagers will be less likely to drink and drive at the end of the night. But even without parental help, teenagers are able to rent rooms on their own. ''We are disinclined to discriminate by age," said Lucy Slosser, a spokeswoman for full-service Marriott hotels in Greater Boston. ''For hoteliers, it's a real quandary. It all comes down to conduct." Marriott hotels have not had a problem with underage parties, she said.

Counselors and police worry that when the trend includes parental complicity, it sends the wrong message -- that underage drinking is OK as long as no one gets behind the wheel. It leads directly to incidents like the Rockland party, where police reported heavy drinking of beer and hard liquor, and found marijuana and heroin. Authorities were called in because of a reported fight that involved someone holding a pellet gun to a teenager's head.

''What we often see is that parents just don't view drinking as a serious issue," said Caitlin Thomas-Henkel, a social worker who directs a substance abuse prevention program in Stoughton. ''They just don't realize that underage drinking is not OK in any form."

Too many adults see drinking as an inevitable rite of passage for teenagers that should be closely monitored but not categorically prohibited, substance abuse counselors said.

In the Rockland Radisson incident, five adults -- a 31-year-old and four men in their early 20s -- were charged with providing alcohol to minors, authorities said late in the week. All five pleaded innocent.

Police officers said they work closely with local hotel managers to prevent underage parties in their rooms and suites -- Quincy Police Chief Robert Crowley said local hotels have ''been on their A game" in notifying police about room parties -- but that, beyond noise complaints, there's little way to know they are happening.

Substance abuse counselors said they were not surprised by the reports of the party; after all, it's unfortunate but established that teenagers are prone to binge drinking and that alcohol use often leads to other substance abuse.

Harrington called parents who provide teenagers alcohol and a place to drink it ''incredibly irresponsible." He urged them to take a no-tolerance stance. provide teenagers alcohol and a place to drink it ''incredibly irresponsible." He urged them to take a no-tolerance stance.

A recent survey by the Century Council, a group funded by the liquor industry that fights underage drinking, found that 65 percent of teenagers obtain alcohol from family and friends, with or without permission. An American Medical Association survey of teenagers ages 13 to 18, released in August, found that nearly half reported having obtained alcohol at some point. Two out of three teenagers said it is easy to get alcohol from their homes without parents knowing about it, one-third said it is easy to obtain alcohol from their own parents knowingly, and one in four teenagers have attended a party where minors were drinking in front of parents.

Police were called to a fifth-floor suite at the Radisson Hotel at about 9:40 p.m. last Sunday after a parent complained about a teenager being beaten at the party. Police arrested 34 people, all but two of whom were under the drinking age of 21. Most of the partygoers, who were mainly from Boston, Weymouth, and Braintree, were charged with disorderly conduct and underage drinking, and some were charged with drug offenses, police said.

They were arraigned Tuesday in Hingham District Court. All pleaded not guilty and were released.

In Stoughton, Thomas-Henkel meets regularly with middle- and high-school students to let them know that, contrary to popular belief, not all teenagers drink. In fact, 63 percent of Stoughton students reported in a recent survey that they had not consumed alcohol or drugs in the past month. That realization makes it easier for them to resist peer pressure and abstain from drugs and alcohol, she said. ''Perception is reality."

Nationally, alcohol use has declined among American teenagers for the past several years, according to the annual ''Monitoring the Future" study on teenage behavior released in December. In 2005, 17 percent of eighth-graders, 33 percent of 10th-graders, and 47 percent of the 12th-graders said they had had alcohol in the previous month.

Carlos Ramos, 17, a Stoughton High School senior, said he rarely goes to parties where beer is flowing, but when he does, he feels secure in his decision not to partake. But he said fears about drunken driving convinces some parents to organize parties in homes or hotel rooms so they know their children's whereabouts.

''I think that's a good idea to a certain extent," he said. ''If no one's driving and it's under supervision, it's better than not knowing where your kids are."

It also carries potential legal consequences. A Plymouth man may face criminal charges of serving alcohol to minors at his home the night of a November canoeing accident that killed two people.

Ramos said he was surprised by the size of the Rockland hotel party and by the presence of illicit drugs, but he said large beer parties are regular high school events, usually when someone's parents go out of town.

In Westwood, school officials began testing high school students with a Breathalyzer at school dances this spring to crack down on underage drinking. The policy has been effective, said School Committee member Josepha A. Jowdy. But no matter how much adults want to protect teenagers, they are going to gravitate toward fun and risky behavior, she said.

''I would love to keep all children in a bubble until they're 25," she said. ''But, unfortunately, we can't do that."