The tape was reportedly recorded inside Sandridge Elementary School in Chicago Heights, Illinois.
The principal and a science teacher, who were allegedly in the video, have resigned. Parents were sent DVDs of the tape Wednesday and Thursday, just days before a school board election.
Parents of students at the school met Thursday evening
"Where is she supposed to be?" asked parent Kim Grivakis. "We have tons of needy children. But no, she'd rather be with the principal bumping and grinding."
The tape was allegedly shot in the principal's office during the day and evening on five dates ranging from late December to early March.
"How can I sit at home knowing my kids are at school when this is going on?" asked parent April Lopez.
Cook County Sheriff's Department officials met with school officials at the school Thursday night and the tape was under investigation.
"We have to see if there were children at school at the time," said John Palcu of the Cook County Sheriff's Department. "If it is, we take it to the state's attorney, let them decide if there's criminal charges available -- maybe official misconduct."
The school's attorney said the matter was under investigation.
School board officials said they became aware of the incident Thursday morning, and the two school employees resigned soon after.
Parents have planned a protest for Monday morning, adding that the resignations were not enough.
"We don’t want their resignations," said one parent, Janet Collins. "We want them fired, we want their licenses stripped. We don't want them to go into another school and do this."