Christopher Metcalfe, 70, from Blidworth in Nottinghamshire, was found not guilty of raping a teenage girl.
At Derby Crown Court he was also cleared of indecently assaulting a nine-year-old girl at a school and another young girl on his farm.
The jury was discharged after failing to reach verdicts on two other indecent assault charges involving those girls.
Mr Metcalfe, who taught rural studies at a residential home near Mansfield, had denied all five charges he was facing.
The case has been adjourned until 27 April.
A retired teacher has been cleared of sexually assaulting three girls in the 1970s and '80s.