Vincent Kiejzo, 36, faces up to two decades in prison when he is sentenced in April, the US Attorney for Massachusetts said.
Police raided Kiejzo's home in September 2020, where they found a USB drive plugged into a television in his bedroom that contained websites dedicated to child sexual exploitation material as well as more than 6,000 images of the material, the prosecutor said.
Some of the photos and videos involved infants, investigators said.
Kiejzo, who was a teacher at Memorial Elementary School, was placed on administrative leave as soon as the charges were announced and later fired, authorities said.
Along with his teaching, Kiejzo was also a swim instructor for 19 years through the Milford Community School Use Program until his arrest.
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