Magnolia ISD Chief Communications Officer Denise Myers said the incident occurred on Thursday during school hours at Magnolia Intermediate School.
"We are proud of how our teachers and students followed procedures and evacuated the building promptly as instructed," Myers said.
In a letter shared with Eyewitness News, the district confirmed that the educator's vaping set off a fire alarm that prompted the entire school to evacuate.
District leaders said that the teacher resigned due to disrupting the entire campus and failure to follow the employee handbook.
Myers added that the district will cooperate with law enforcement on the incident.
A substitute teacher will replace the teacher in the classroom as the school wraps up the school year, Myers said.