A private school teacher in Melbourne's north-east has been charged by police after his colleague allegedly found child pornography images on a school computer.

The teacher from Catholic Ladies College in Eltham was arrested and charged late last week after the inappropriate material was discovered by another member of staff.

Detectives from the Banyule crime investigation unit charged a 30-year-old Hillside man with one count of knowingly possessing child pornography, a police spokeswoman said.

In a letter sent to parents on Monday evening, principal Stephanie Evans said she contacted police as soon as the matter was drawn to her attention.

The teacher was immediately suspended from work.