Cleveland ISD said at about 10:24 a.m. that classes had resumed as scheduled.
The school first posted about the lockdown at about 8:30 a.m.
According to Cleveland ISD, a student was arrested and removed from class after district officials received an anonymous tip indicating that the student brought a weapon to school. The campus was immediately placed on lockdown.
A nonfunctioning "look-alike" weapon was found and confiscated within 20 minutes of receiving the tip, the district said.
The student was arrested.
"Cleveland ISD takes all threats seriously. Cleveland ISD applauds the student who alerted staff to the fact that someone had potentially brought a weapon to school and the school administration for their quick actions. Although the confiscated weapon was a "look-alike," the district is treating the situation with the same level of intensity as if it were real," a statement read.
The district said any students found to be involved with the incident will face disciplinary action.