|Gilgil is about 100 kms north-northwest of Nairobi|
Birmingham Crown Court heard he would lure boys to his house in Kenya by offering them food, shelter and money.
Harris, 55, of Pudleston, near Leominster, Herefordshire was cleared of 10 further charges, including rape.
The jury failed to reach a verdict on one remaining rape charge. He will be sentenced in the new year.
Before the trial, Harris also admitted six offences of indecent assault against three boys aged between 13 and 14, when he was a teacher at Shebbear College, Devon in the 1980s.
|Harris would drive into the town of Gilgil and offer street children |
food and money to go home with him
"He was a predatory sex offender who, over a number of years, groomed and exploited children and those around him in order to perpetrate his abuse," he said.
Harris had faced 23 charges in total, including 18 allegations relating to assaults.
|Harris was active in Kenya from the 1990s until 2013|
During his trial prosecutors said he lured homeless boys to his home, known locally as "The Green House", by offering them food and shelter.
The court heard he would drive into Gilgil and encourage them to get into his Land Rover, with food and money.
One man who claimed he had been raped by Harris as a child, committed suicide shortly after giving evidence.
Michael Kamondia was among several boys to testify across a live video link from Kenya but died on December 7, days before the jury retired to consider verdicts.
|Harris was head of the gap-year charity VAE, |
which placed British volunteers in Kenyan schools
The abuse came to light when a Channel 4 documentary team making a film about the plight of Gilgil's street children was given information about his activities.
Harris was prosecuted using legislation that allows British citizens to be tried for sex offences committed abroad against children if it is also an offence in that country.
|Harris committed offences at his property near Gilgil, known as "The Green House"|
Current head teacher Simon Weale said the school acted promptly at the time to report the allegations to police after the victims made complaints. Harris was suspended and left "during the course of the investigations", the college said. So, the police dropped the investigation because he left? Really? 25 to 30 years of child abuse could have been prevented. How dreadful!
"Even though these offences took place more than 25 years ago, we utterly deplore these crimes and our overwhelming sympathies are with Harris' victims," said Mr Weale.
Harris had originally faced 22 charges relating to assaults in Kenya, but Judge Philip Parker QC told jurors four had been removed from the indictment mid-trial.
The case was nearly thrown out after Channel 4 published a news item wrongly stating he had already been convicted, only hours after jurors began deliberating.
Judge Philip Parker QC said he regarded the broadcaster's mistake as "beyond unfortunate".
The matter has been referred to the Attorney General to consider possible action under contempt of court procedures.