Texas school districts can secure their schools if they choose.... whether is securing entrances/exits, hiring armed security, allowing staff/teachers to carry... whatever. It's up to the people who live there to decide. Only about a third of Texas school districts will even allow staff to carry... so... it is what it is.
Texas:
https://www.star-telegram.com/news/state/texas/article261779287.html
About 365 school districts in Texas allow staff to carry firearms on school premises. They represent about 36% of the 1,023 independent school districts in Texas. In 2013, the Texas Legislature passed two methods to authorize employees to carry firearms on school property. Texas school districts are able to opt into: the Guardian Plan and the School Marshal Plan. The School Marshal Program allows marshals designated by a district to be armed. Since 2013, Texas law has permitted school districts to appoint one or more specially trained and licensed employees as school marshals. Those school marshals can carry a handgun on the school premises after 80 hours of training. School marshals are restricted from carrying concealed firearms if they’re in regular contact with the students. In that case, the marshal can have a gun in a safe at the school. Schools can appoint one marshal per 100 students in average daily attendance, or for a private school, one marshal per 100 students enrolled. “The board must require that a designated school marshal may carry a concealed handgun on the marshal’s person or in a locked and secured location on the physical premises of a school,” says the Texas Association of School Boards. “A school marshal may access a handgun only under circumstances that would justify the use of deadly force for the safety or protection of others as provided by law, and the marshal may use only frangible duty ammunition approved for the purpose by [Texas Commission on Law Enforcement].” The Guardian Plan is broader, authorizing school boards to allow any employees to be armed, under the authority of the federal Gun-Free School Zones Act and the Texas Penal Code. Those employees, after completing 16 hours of training, may carry a concealed firearm in the presence of students. “In most cases, school districts limit employee authorization to commissioned peace officers. In some districts, however, authorization has been granted to other school officials or even classroom teachers,” the TASB report says. “While state and federal law gives school districts broad discretion to authorize the possession of firearms and other weapons on school premises, granting such authority brings a host of practical concerns, including safety and liability.” A Texas school district has the option to appoint one or more armed school marshals, adopt a local policy that authorizes employees to carry firearms on school premises, or both, according to the TASB. Only a few districts have chosen the School Marshal plan and instead opted for the Guardian Plan. As of 2018, 303 school districts had adopted the Guardian Plan, according to the TASB. And there are currently 62 school districts participating in the School Marshal Program, the Texas Commission on Law Enforcement told the Star-Telegram.