Two Plainview Independent School District buses, operated by First Student School Bus Transportation Services, were rented over the weekend.
Superintendent Ron Miller said Monday the buses were used by Texas Tech students.
Bonnie Bastian with First Student, which provided the drivers, said alcohol is never allowed on district-marked school buses.
Beta Theta Pi's Ryan Vissotzky says the "shot buses" were used to transport members to events at other locations before the fraternity Christmas party. Vissotzky said buses were rented "to keep everyone safe."
A neighbor called police about apparently inebriated students getting off a school bus and carrying cups that allegedly contained booze.
Plainview is 40 miles north of Lubbock.