Former Maris Stella High principal Anthony Tan Kim Hock was packed off to jail for five months on Friday after the High Court dismissed his appeal against conviction and sentence for embezzlement.
Last year, Tan, 66, was sentenced to five months' jail after a district court found him guilty of criminal breach of trust for misappropriating school funds of about $68,000.
The Marist Brother used the money from a school chapel-building fund to renovate Champagnat House, the residence of his Catholic order in Flower Road.
The money paid for granite surfacing on walls, stained glass windows and kitchen appliances.
Tan appealed against his conviction and sentence. The prosecution also appealed, arguing that his jail term should be doubled to 10 months.
At his appeal last month, his lawyer Peter Low criticised the trial judge for excessively intervening in the proceedings, creating the impression that he was not impartial.
Mr Low argued that Tan had no dishonest intention when he used school funds to pay for the renovation works, as he believed the money belonged to the Marist Brothers, who set up the school.
Deputy Public Prosecutor Kwek Chin Yong had argued that the funds belonged to the school, which is not directly linked to Champagnat House.
On Friday, Justice Chan Seng Onn dismissed appeals from both sides, upholding the trial judge's decision.