Just how safe can police make a school?

Would it have made a difference if a police officer had been stationed at Lincoln-Sudbury Regional High School last week?

That's one of many questions raised in the wake of Friday's fatal stabbing of a Lincoln-Sudbury student, with some parents criticizing school officials for not taking steps to tighten security.

A fellow student, John Odgren, 16, has been charged with first-degree murder in the death of 15-year-old James F. Alenson.

Area police say officers stationed at schools are in a position to pick up on potential trouble.

"Obviously things can erupt very quickly without people knowing anything about it," said Lieutenant Paul Shastany, with the Framingham Police Department. "But that early warning prevents deaths and tragedy. Many problems have been resolved prior to a crisis stage. We think a lot of these things are preventable."

The Framingham department has one officer assigned full time to the high school and one for the middle school and elementary schools. Newton, Framingham, Watertown, and Waltham are among communities that have school resource officers. Lincoln-Sudbury does not have one.

Rick Johnson of Sudbury, who has a son in ninth grade at Lincoln-Sudbury, said he was upset that school officials have yet to explain how they'll tighten security.

"It's like a college campus. They go where they please; there's no security ," he said.

Johnson said he questioned Lincoln-Sudbury's principal, John M. Ritchie, on Sunday about long-term measures but did not receive specific answers. Ritchie is also superintendent of the regional school district.

"They're concentrating on grief counseling instead of addressing parents' concerns about long-term security," said Johnson. "We're very worried about this."

Alan Crosby of Sudbury, who has two sons at the high school and a daughter who graduated in June, suggested that parents and school officials reconsider its traditionally open campus, with juniors and seniors allowed easy access to come and go.

"Somewhere, something has to give," said Crosby, adding that he's not happy to hear that some school officials and police are declaring the school is safe.

He said he doesn't favor a campus lockdown or posting a police officer, but he would like to see a policy that recognizes that not all students, especially those with special needs, can handle the freedom of an open campus.

Sudbury Police Chief Peter Fadgen and Sudbury Selectman Larry O'Brien both said they don't think having an officer in the school would have changed the outcome.

"It's an isolated act , and the school is so big that it could happen no matter if there were five police officers there," Fadgen said.

Ritchie agreed: "I don't think it would have made any difference that day because the incident was so sudden and unpredicted and proceeded by nothing that any of us was aware of."

But the principal said school officials would consider stationing an officer at the school. "Once we get through this grieving phase, we'll take a look," he said.

Shastany said resource officers can serve to break student stereotypes of police.

"Police officers, frequently in children's lives, have been seen as a malignant authority figure. The only time people encounter police is when there's a problem," the Framingham lieutenant said. "Now, when an officer in school wearing a uniform is seen . . . helping kids, it turns the concept of authority from negative to positive."

Framingham officers have trained school resource officers in five area communities, including Ashland, Holliston, and Southborough.

Because Framingham High School is one of the larger high schools in the state, resource officers carry cellphones as well as personal digital assistants with the names and photos of every registered student, said Shastany. Police can access student class schedules in a matter of seconds in order to verify if they're talking to a student or an intruder.

"You can't know 2,100 students, but you can validate and quickly determine where they should be. It isn't Big Brother," said Shastany. The information, combined with tips from principals concerned about absent students, helps officers decide whether to call parents or visit homes.

In Waltham, five full-time officers handle the city's public and private schools. Two officers are at Waltham High School and one at each of the city's three middle schools, said Captain William Stanton .

The officers' duties range from visiting bus stops to breaking up playground fights to investigating reports of a student bringing a weapon to school. "They're busy, believe me, they're busy," said Stanton.

Police also attend school dances and major sporting events, such as the Waltham-Brockton football game, where things could get out of hand. Because the resource officers know students and keep up with the scuttlebutt, they can assist uniformed officers and alert them to potential trouble, said Stanton.

"When they're not there, the principals are calling to say, ' Where are they?' " said Stanton.

He also said Waltham officers attend a conference every fall and workshops held year-round by the Middlesex district attorney's office to address such issues as bullying, battering, drugs, and behavioral disabilities, including autism.

A number of school resource officers said they keep tabs on websites popular with students, such as MySpace.com and Facebook.com, looking for threats or risky behavior like young teens lying about their age or posting inappropriate photos.

Officer Keith Kasprzak, the resource officer for both public and private schools in Weston, uses a laptop to monitors the websites under an assumed name. "It's been a good tool for some things," like tracking vandalism and for learning about large parties and potentially dangerous behavior.

In Framingham, police only go online if they've received a tip about a threat. Otherwise, Shastany said , they leave monitoring computer use to the parents. "We don't want people not to trust the officers."

That's a concern echoed by Lieutenant Bruce Apotheker, who oversees Newton's community services division and the city's four youth officers.

"The most important thing is building a rapport. If a kid can trust you and believe in you, all sides win," Apotheker said.

Both Newton North and Newton South high schools have a plain clothes officer at an office on -site virtually full time, said Apotheker. The other officers cover middle and elementary schools.

Police differ over whether to have school officers work in uniform or dress casually.

R. Vincent Springer, Needham's school resource officer, said that by wearing a police golf shirt and dress slacks with his police belt, students are less intimidated to approach him. "The goal is to get the kids to see me more as a human being than a disciplinarian," he said. "I still want to be identified clearly as a police officer in case we need back up."

For Wellesley, Weston, and Framingham officers, wearing the standard police "blues" helps students learn to "not be afraid of the uniform," said Weston's Kasprzak .

Many police officers say the work they do outside of the school day often pays the greatest dividends, such as sponsoring sports events or offering a police academy for children. They say the goal is to establish a bond of trust and friendship between officers and children that police hope will head off problems when the children get older.

In Wellesley, officers coach T-ball games and the girls' "powder puff" football game against Needham every Thanksgiving. Police also serve on the town youth commission .

"The contact, talking to the kids, hopefully be in a position of influence for them," resource officer Brian Spencer, who covers all the schools, said in describing his job. "Sometimes you don't even know who you're reaching."

In Franklin, off-duty officers volunteer their time coaching youth sports. Dan MacLean, the district's school resource officer, serves as the head coach for the Tri-County Regional Vocational High School football team; a detective is the assistant coach. Another officer is the hockey coach, and a detective coaches the freshman basketball team at Franklin High School, he said.

"Having a police officer in the school definitely helps," said MacLean. "Kids see us all the time."

Many departments say that tight budgets prevent them from placing officers in schools or turning part-time postings into full-time jobs .

"There's no money for policing," said Wrentham Police Chief Joseph Collamati. "We're on a wing and a prayer. If we could afford to, we'd love to do it.

Collamati said the town's resource officer spends 10 to 20 hours a week at King Phillip Regional High School, which serves about 1,200 students from Norfolk, Plainville, and Wrentham. "He's our eyes and ears at the school. He's got his hands full down there." the chief said.

Thomas Scott, executive director of the state Association of School Superintendents, said while he thinks school resource officers are "very valuable" and generally welcomed by school leaders, he doubts the presence of an officer at Lincoln-Sudbury would have prevented last week's killing.

"That's about as tightknit a community as one could expect at a school," he said. "Teachers and kids have such warm relationships and talk to one another with ease."

Christina Pazzanese can be reached at cpazzanese@globe.com.