The teacher, whose name has not been released, told investigators he did not see any of the acts that authorities suspect occurred last week.
"He's saying he has no knowledge of the reports, and we have to see how we can reconcile these stories and reconcile them," said Troy Flint, a spokesperson for the Oakland Unified School District.
"You have a beautiful principal here who holds her school down. I can just say it was the ignorance of that teacher," said parent Lataya Young.
The teacher was barred from campus at least until the investigation is completed.
Meanwhile, the students believed to be involved in the sexual acts were not accused of any wrongdoing.
The Associated Press contributed to this report.