Jitendra Prasad Tahal, a former dental worker from Auckland, entered guilty pleas to three charges of indecent assault in the Manukau District Court.
He was bailed until sentencing next month and copped abuse from people in the public gallery as he left.
Tahal admitted indecently assaulting the girls, aged in their mid-teens, between June 2012 and July last year.
Police have said the crime took place on school grounds when he visited there as part of his work, NZ Herald reported.
According to police, Tahal was not directly involved in providing dental treatment but had contact with some of the student.