According to court records, the student who found the camera told school officials she was dressed only in a bra and panties when she noticed two separate boxes in the changing room that had holes for the cellphones' camera lenses, according to the Times.
One of the devices was actively recording when it was discovered by the student, WTSP reported.
Ackett was charged with one count of video voyeurism and was released Sept. 12 after posting a $7,500 bond.
According to the Sheriff's Office, Ackett's cellphones were seized during the initial investigation and a search warrant was obtained and served on the devices, WTSP reported.
Analysis of the phones revealed 267 videos and images of girls ranging in age from 14 to 18 in various stages of undress, WFLA reported.
Ackett resigned after his first arrest after a 27-year career in the school district. He is married with two teenage boys, the Times reported.