SAN ANTONIO – Several Northside Independent School District campuses were placed on lockdown Friday after a shooting at Lackland Air Force Base. District spokesman Pascual Gonzalez said lockdowns occur almost on a daily basis at any of the district's 120 schools.
Valley Hi Elementary, which is closest to Lackland, as well as Allen Elementary and Rayburn Middle School were affected by Friday's deadly shooting.
Gonzalez said the district is affected each time it's notified that law enforcement officials are searching for a suspect in a neighborhood or handling a domestic disturbance or other scenarios.
He said the district responds immediately. No one is allowed in or out of the school until they're given the official all-clear.
"They get under desks, get in a corner, turn off the lights, close the blinds and curtains, and remain quiet," Gonzalez said.
Even phones and devices are turned off, said Andrew Morris, principal of Valley Hi Elementary, in a letter he sent home to parents on Friday. Click here to read the full letter.
Also, classroom doors are not unlocked until teachers get the proper code.
Gonzalez said teachers then must try to explain to their students what occurred.
WATCH: Valley Hi parents notified of lockdown via social media
"The teachers tell the kids what they need to know, at the time they need to know it, in terms they will understand," Gonzalez said.
In addition to social media, he said notifying parents by phone, using the school's messaging service, depends on when they have information to convey.
"Our priority is always to tell the parents whatever we know, as soon as we know it. But we won't talk until we have solid information," Gonzalez said.
Click here to read more about Friday's shooting at Lackland AFB, in which two people died in an apparent murder-suicide.