They came to save the future, they said, to debate late-night loitering, drugs, violence, music, danger, chaos, time, proper sleep, good grades, government authority, parental duty, hanging out, going home, being reasonable, and -- the generation gap widened on this point -- whether the Constitution guarantees the right to go-go all night.

"What we're concerned about today," D.C. Council member John Ray (D-At Large) told the large, apprehensive crowd in the council chambers, "are bodies filled with good tunes but heads filled with nothing."

During a seven-hour public hearing yesterday, city officials, community groups and teen-agers discussed a bill before the council.

If passed, the controversial measure would require owners of late-night clubs in the city, specifically dance halls presenting go-go music concerts to thousands of teen-agers each week, to bar minors after 11:30 p.m. on weekdays and after 1 a.m. on weekends.

About 100 high school students attended the hearing, filling the room with colorful sweaters and worried faces. They clutched rumpled petitions filled with classmates' names, snickered when council members spoke about the trouble that go-go music clubs are alleged to attract, proudly read prepared statements or finished homework as they listened to the proceedings.

More than 40 people testified to the council's committee for Consumer and Regulatory Affairs about the bill, which is expected to be brought to the full council in about a month. Council member Frank Smith Jr. (D-Ward 1) proposed it this year after repeated shootings and stabbings outside of District go-go music performances, which often do not end until 3 a.m. Much of the testimony yesterday focused on Celebrity Hall, a go-go music club on Georgia Avenue NW. A teen-ager was fatally stabbed as he left a concert there early Sunday, according to police.

Responding to that incident, which has further outraged those who claim the music halls create a dangerous public nuisance, Smith began the hearing by announcing plans to curb trouble associated with go-go concerts. He again urged parents to forbid their children to attend the late-night concerts. He asked Mayor Marion Barry to create a task force that would develop alternative social events for District youth, and to issue an executive order requiring dance hall promoters to register a major event with District police five days before it is held. He also called for a meeting of District go-go owners.

Those opposing the bill ridiculed it as merely a Band-Aid solution. They said it would hurt go-go music, but do little to reduce drugs and violence on city streets. They wondered how the bill could be enforced, and said most trouble is caused by young adults, not minors.

"Parents should be the ones to tell us what we can and can't do," 15-year-old Dori Williams, who held a petition of 127 names who opposed the bill, said as she listened to testimony. "They {council members} just have the wrong idea. It won't work."

"What are they {owners} going to do, stop a concert and ask everyone for an ID?" Vincent Cohen, a senior at Sidwell Friends School, asked.

Other students, however, hailed the bill as an important first step toward more peaceful communities. "No young person has to be on the street at 4 a.m.," said Don Turner, 17, a senior at Calvin Coolidge High School. "Most people just go to those concerts as a social event, not for the music. You'll see hundreds outside even when the concert is going on."

Council members applauded the students who testified. But they asked students who opposed the bill if they also believed truancy, drinking and driving laws for youths also should be abolished. "If you all were going to get rid of those laws under that same logic," Smith told a group of testifying students, "allow me to have until sundown to get out of town."

Some speakers charged that the bill, if passed, would violate teen-agers' constitutional right to assemble whenever they choose, and argued that restricting minors' access to the popular clubs after a certain hour was simply "asking kids to be more mischievous on the streets."

Bill proponents emphasized a direct link between staying out all night and poor academic performance, and said forcing minors out of go-go clubs earlier would be a significant step to help them in school. "After all," said one speaker, "it's not how long you go-go, but how well you go-go."