Marinko Jankovic was a business management and commerce teacher at Berwick Secondary College when he placed the camera on the floor near his desk and had girls come to the front of the class so he could film under their skirts.

He recorded almost 140 images of girls aged between 11 and 17, over 26 months between 2011 and 2013, but police are unsure how many girls he filmed as it was impossible to identify his victims.

Jankovic was in June jailed for six months by a magistrate after pleading guilty to representative charges of knowingly producing child pornography and possessing child pornography, but spent only two hours
in custody before he appealed against the sentence.

But County Court judge Graeme Hicks on Thursday upheld the sentence imposed by magistrate Julie O'Donnell and jailed Jankovic, who must also serve a two-year community corrections order once released.

"This was a grave breach of trust," Judge Hicks told the 61-year-old.

"You were the students' protector yet you exploited them for your own sexual gratification."

Defence counsel Rohan Lawrence had argued a jail term was not warranted given Jankovic has kidney disease and is in poor health, made an early guilty plea, was remorseful and was of otherwise good character, and because the images were at the lowest level of child pornography.

Police discovered Jankovic's offending when his laptop was seized by the school's principal in March 2013. He was immediately suspended and was later sacked and has been unemployed since.

But Berwick Secondary College did not inform students and their families of the offending at the time, and the issue only became public this year when the Department of Education offered counselling to Jankovic's former students.

The court heard Jankovic also took the pen camera around his classroom and positioned it and himself so he could film under the girls' clothing while they sat at desks. He also filmed down some girls' tops.

Mr Lawrence said Jankovic was stressed at work when he began offending and bought the pen camera so he could record acrimonious discussions with the school's vice-principal.

Judge Hicks said it was ironic Jankovic felt there had been a breach of trust towards him, and agreed with prosecutor David Gray, who said the offending had been predatory, protracted and involved a large number of victims.