In Arlington, 20 city-employed school resource officers work with junior and high schools and assist elementary schools as needed.
In the Northwest district, seven school resource officers work at high schools and middle schools and are available to elementary schools.
Northwest also has an agreement with Denton County law enforcement to provide additional officers throughout the district when issues arise.
Roanoke provides support at the district's Steele Accelerated High School and Roanoke Elementary, said Lesley Weaver, the district spokeswoman.
But until now, Texans have generally drawn the line at posting armed officers at elementary schools.
"The kids are going to think something is wrong," said Juan Zamudio, whose 4-year-old attends Birdville Elementary School in Haltom City.
Zamudio was shaken when his daughter's elementary school went into lockdown recently.
The idea isn't new.
"It was discussed after Columbine. It was discussed after Jonesboro," said Kevin Lawrence, executive director of the Texas Municipal Police Association in Austin. "It's not the entire fix. It might be part of the fix."
Posting armed police at elementary schools might ease worries.
Tison said: "Peace of mind and freedom to use their talent to teach children without undue stress are reasons to consider armed officers at campuses. It is a much better alternative than the idea of allowing licensed administrators and teachers at local campuses to carry guns."
Steven Poole, executive director of the United Educators Association, said he worries that communities may overact.
"These are neighborhood schools, and we want to be welcome and inviting for our parents and students," Poole said.
Who will pay?
The biggest roadblock, however, could be money.
Can cash-strapped schools and communities realistically pay for armed officers in every elementary school? In Texas, that is 4,600 campuses.
Sgt. Steve Hall, president of the Fort Worth Police Officers Association, estimates that it would cost $5.5 million just to place one armed peace officer at 81 elementary schools in the Fort Worth district.
Fort Worth schools pay for half the security services in the district.
This year, that comes to about $3 million for Fort Worth police and $154,400 for Benbrook police.
But security dollars compete with other needs -- like reading, writing and math.
"At the state level, cuts to local districts have already hampered their ability to provide an adequate level of instruction," Tison said. "If national and state government is willing to provide financial support to districts for instruction and security, the local districts will find appropriate solutions."
Tobi Jackson, a Fort Worth school trustee, said money is needed for threat assessment and mental health support for schools and communities.
"If we educate our community members and students to recognize and report those individuals embroiled in severe personal conflict or who are deeply troubled, we will be more successful at preventing horrific acts of violence," Jackson said.
"In many instances of school violence, what seemed to be appropriate stopgaps were in place: You had a controlled-access school [Newtown], two armed police officers on campus [Columbine] and campus police on the ground [Virginia Tech], and we still had the tragic loss of human life."
Staff writers Jessamy Brown, Sandra Engelland, Shirley Jinkins, Susan McFarland and Patrick M. Walker contributed to this report.