Former River Valley High School (RVHS) principal Koh Yong Chiah began a four-week jail term yesterday after losing an appeal against his sentence for lying to a Ministry of Education (MOE) officer.

The 61-year-old had falsely claimed that he was not having an extramarital affair with a vendor to whom he awarded millions of dollars in school contracts.

A High Court panel of three judges found that the case justified a custodial term as "appreciable harm" was caused by Koh's offence - even though there was no finding of actual corruption or misuse of public funds.

"By concealing his affair... and passively maintaining the falsehood, the appellant was allowed to undermine the integrity of the procurement process and confidence in the public service, especially since the conflict of interest went undetected for a long period of time," Judge of Appeal Chao Hick Tin said, delivering the judgment.

The court, which also comprised Chief Justice Sundaresh Menon and Judicial Commissioner See Kee Oon, accepted that Koh's motive for lying was not to cover up the procurement improprieties, or to enable the perpetration of more procurement improprieties for his lover's benefit.

Defence lawyer Eric Tin had argued that Koh had lied because he was "overwhelmed by the embarrassment" of being confronted with his extramarital affair.

But the court pointed out that even if Koh was embarrassed, the least he could have done was to remove himself from the position of conflict of interest. Instead, Koh continued signing off contracts awarded to his lover's companies.

Koh, who had been principal of four schools since 1995, gave false information to a senior MOE officer who was looking into an anonymous complaint that he was having an affair with Ms Ivy Loke Wai Lin.

Koh was then principal of Jurong Junior College (JJC) and Ms Loke was a director of a company that was bidding for contracts and provided services to it.

Koh and Ms Loke, now 55, met in 2000 while he was the principal of Chinese High School (CHS). Their first sexual encounter was during a CHS community service trip to Lijiang, China, in 2001. Both were married.

From May to November 2005, as the final approving authority for JJC's contracts, Koh awarded six contracts worth $162,491 to her company, Education Architects.

On Nov 24, 2005, when cluster superintendent Chia Ban Tin asked Koh whether he was having an affair with Ms Loke, he denied it.

After the interview, Koh continued to award contracts to Ms Loke's companies.

As JJC principal, he approved another 48 contracts to Ms Loke's company.

As RVHS principal, he awarded 39 contracts to another of her companies, Education Incorporation.

Between 2005 and 2012, he approved $3.2 million worth of contracts to both her firms.

Koh was dismissed from public service with effect from Sept 14.