Extra security measures were in place Friday for Aldine ISD's Nimitz High School and Nimitz 9th.
Authorities say several threats have been made about a possible fight between some New Orleans students and Houston students.
There was a fight last week that ended with the threat of another fight this week.
An extra 15 officers are expected to be on the two campuses Friday.
School officials say hundreds of students stayed home Friday, possibly because of concern over the threats.