Additional police officers were posted at Klein Forest High and three surrounding schools because of multiple reports of a suspicious person near the school.
The other schools given additional police presence were Wunderlich Intermediate, Greenwood Forest and Kaiser Elementary schools.
No suspicious person had been found on campus by the end of the school day Tuesday.
Klein Forest High conducted a "controlled release" at school's end Tuesday, allowing students to leave campus section-by-section from the school. Students who drove to school were the last ones allowed out, with parking lots monitored until they left.