He already had a wife when he started an affair with a married woman in 2001.
And the woman became a director of one of the school's vendors and of another company providing education-related services and organising overseas learning journeys.
Koh Yong Chiah, who was principal of The Chinese High School, Jurong Junior College and River Valley High School at various points in his career, approved, in a span of seven years, more than $3 million worth of contracts to the woman's companies.
In November 2005, when questioned by a Ministry of Education (MOE) officer following a complaint, Koh denied having an affair with Ms Ivy Loke Wai Lin, now 55.
But he continued to see her and rewarded her companies more contracts.
Yesterday, Koh, 61 and still married, pleaded guilty in court to one count of giving false information to a public servant on Nov 24, 2005.
A second charge of giving false information to the Corrupt Practices Investigation Bureau on Dec 18, 2012, will be taken into consideration during sentencing.
The court heard that Ms Loke was working for the Television Corporation of Singapore (now MediaCorp) in 2000 when she read about The Chinese High School's involvement in community service projects to help the less fortunate in Singapore.
She approached The Chinese High School (now Hwa Chong Institution) to suggest a project involving a village in China.
Koh was the principal of The Chinese High School at the time.
Deputy Public Prosecutor Navin Naidu said Ms Loke met Koh later that year.
He said that "a mutual attraction began to develop between the two of them, which eventually developed into a sexual relationship".
The pair had sex for the first time in China during a school trip in March 2001.
Later that year, Koh bought himself and Ms Loke two white gold rings "as a pledge of their love for each other".
Koh left The Chinese High School in 2002 and became the principal of Jurong JC the following year.
In 2004, Ms Loke separated from her husband and they divorced in 2005.
As the principal of Jurong JC, Koh was the Final Approving Authority for contracts awarded by his school to vendors.
Between May and November 2005, he signed off six contracts to Ms Loke's company, Education Architects 21, for a total worth of $162,491.25.
Ms Loke was also a director of another company, Education Incorporation.
The contracts were for items including overseas trips to Chengdu, China, and Medan, Indonesia.
DPP Naidu said Koh did not disclose the nature of his relationship with Ms Loke to the other members of the JC's quotation approval panel comprising the vice-principal and heads of department.
He added: "In November 2005, MOE's Director General of Education received an anonymous complaint alleging, amongst other things, that the accused was having an affair with (Ms Loke) and that they were behaving inappropriately on school premises and on overseas school trips."
Ms Chia Ban Tin, a cluster superintendent with MOE, interviewed Koh that month and Koh denied having an affair with Ms Loke.
Koh left Jurong JC in December 2009 and became the principal of River Valley High School.
He continued seeing Ms Loke while heading the school and gave her companies business. He left the school in September 2012.
DPP Naidu said that in 2007, 56 per cent of the revenue of Ms Loke's companies were attributable to contracts to provide services for Jurong JC.
By 2011, 90 per cent of Education Incorporation's revenue came from River Valley High School.
DPP Naidu added that Koh would sometimes help Ms Loke to amend some of the details in the itinerary or quotations before they were submitted to the schools for consideration.
In his submissions, DPP G. Kannan urged District Judge Hamidah Ibrahim to jail Koh for between four and six weeks.
He stressed that the case involves "a senior public servant who was dishonest when the conduct of his official duties were investigated".
Koh's lawyer Lawrence Ang pleaded for his client to be fined instead. In his mitigation, he said Koh made no financial gains and "no one suffered any loss".
Koh, who broke down when he addressed the judge yesterday, said that he felt very ashamed.
Wiping away his tears, the father of two said: "I hope Your Honour will show me mercy so I can live my life with dignity." Koh is out on a $10,000 bail and will be back in court on Jan 7.
He declined to speak when The New Paper approached him yesterday.
Responding to queries from TNP, MOE said Koh is currently suspended from duties.
Its spokesman said: "Educators who fail to comply with our standards of conduct and discipline will be subjected to disciplinary action. For serious cases, they may be dismissed from the service."
For giving false information to a public servant, Koh can be jailed up to six months and fined up to $1,000.
Koh Yong Chiah joins Ministry of Education.
Koh becomes principal of The Chinese High School.
Koh meets Ms Ivy Loke Wai Lin.
Koh and Ms Loke have sex during a school trip to Lijiang, China, in March.
Koh leaves The Chinese High School.
In January, Koh becomes principal of Jurong Junior College.
Between May and November, Koh awards six contracts worth $162,491.25 to Ms Loke's company.
MOE receives complaint about Koh's affair in November.
On Nov 24, MOE officer interviews Koh, who denies the affair.
In December, Koh becomes principal of River Valley High School.
Koh leaves River Valley High School in September.
From November 2005 to 2012, Koh approves 87 more contracts totalling $3.2 million to Ms Loke's companies.
This article was first published on Dec 19, 2015.
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