The D.C. Council agreed Tuesday to increase behavioral health services and testing for city youths to try to keep students in schools and out of jail, but officials caution that the District still has to find money to pay for some key provisions of the bill.

After two years of work, the council tentatively approved a broad series of reforms in response to a March 30, 2010, shooting spree that killed four youths and injured six others in Southeast Washington.

Five men are on trial in the shooting, which District officials said exposed major gaps in efforts to preemptively address mentally unstable or violent youths.

The bill, a top priority for council member David A. Catania (I-At Large), calls for an extension of mental health services to all public and charter school students, including those in pre-kindergarten and Head Start.

The District also will implement new truancy rules, mandatory behavioral health screenings for youths in the juvenile justice system and a citywide study to evaluate the mental health needs of District youths.

By the 2016-17 school year, the bill mandates that all students have access to mental health professionals in school. Currently, one in three District schools offers in-school behavioral evaluation and care.

The council unanimously approved the changes Tuesday, but it must vote on the legislation a second time later this month. Mayor Vincent C. Gray (D) is expected to sign it.

“This will represent the most comprehensive behavioral infrastructure in the country,” Catania said. “It represents two years of thoughtful engagement of the stakeholders to try to come up with something that will materially advance the well-being of our young people.”

One of the city’s worst mass shootings in decades came in March 2010 after teenagers gathered at a house party after a funeral in Southeast Washington. Some walked a few blocks away to South Capitol Street SE, and gunmen, allegedly armed with assault-style weapons and semiautomatic pistols, opened fire.

Police said the shooting capped a spiral of violence set off days earlier by the disappearance of a gold-colored bracelet.

The shooting shocked city leaders, some of whom questioned whether it could have been prevented if school and law enforcement officials had been more adept at spotting potential mental health problems.

Nardyne Jefferies, whose daughter, Brishell Jones, was killed in the shooting, helped the council draft Catania’s bill.

But some provisions of the bill may be implemented only if city finances improve.

In a statement to the council, Chief Financial Officer Natwar M. Gandhi warned that there is not enough money in the city’s spending plan through fiscal 2015 to fund the bill.

Gandhi estimated that the bill will cost taxpayers almost $23 million over the next three years, which will require Gray and the council to prioritize the initiative when they make spending decisions later this year.

The biggest cost — about $20 million over three years — will be for the expansion of mental health and truancy services to all schools, Gandhi said.

Gandhi said he is concerned that many charter schools do not have enough resources to pay for the changes.

But Catania and several council members argued that the city will have to find the money to pay for the changes, noting that some of the costs stem from the school system’s failure to fulfill existing legal requirements.

Among other changes, the bill requires an “analysis of the root cause” of bad or truant behavior and mandates that the school system connect the student with needed services.

“Parents are screaming out for resources to help their children, and they don’t exist,” Catania said. “This is going to be an expensive proposition, but we ignored it long enough.”

Last year, 20 percent of D.C. public school students had at least 15 unexcused absences, council officials said. Under current rules, students are permitted up to 25 days of unexcused absences before they are referred to truancy court. The bill reduces that number to 20.

Lee F. Satterfield, chief judge of the D.C. Superior Court, worries that the change could result in too many students clogging the federally funded D.C. court system.

“We would have to add several staff members in order to meet the expected increase in the volume of referrals,” Satterfield wrote. “We propose delaying the effective date . . . pending the Congress appropriating sufficient funds to the Superior Court.”

Council member Marion Barry (D-Ward 8) countered that lawmakers have to act to prevent another “atrocious, terroristic act.”

“Someone who takes a gun on a whole group of people must have psychological problems that must be addressed,” Barry said.