A ninth-grade student was arrested just before 9 a.m., according to the district. All other students and staff are safe.
The district says they were made aware of reports of a gun by other students who spotted possible threats mentioned on social media.
According to the Galveston County sheriff, the teen will likely face the charge of illegal possession of a firearm in a prohibited area.
The lockdown has been lifted and the district says they were searching for ammunition around the school, but none was found.
Authorities searched the school as a precaution and as part of their protocol.
Parents picked up around 60 kids after the lockdown was lifted at the school.
The unloaded gun scare comes one day after at least 19 students and two adults were killed in an elementary school shooting in Uvalde, Texas.
A separate situation happened Wednesday morning at George Ranch High School, according to Lamar Consolidated ISD.
The school is currently "on hold" as a "student disruption" is addressed, the district says.