Taha Jalo Murad said the terror group tried to indoctrinate him and his classmates into becoming extremists.
"Taha's ordeal began when ISIS took over his school in Kocho village, in the Sinjar Mountains, northern Iraq."
They told the teenagers they would help form an army that would march on Rome and ultimately defeat the US.
The boys told precisely where to hold the knife on the neck during a beheading.
After instruction they were forced practice on fellow pupils at the front of the class in mock executions.
Speaking exclusively to MailOnline, Taha said: 'They taught us how to cut people’s heads off - they taught us which arteries of the neck are best to cut.'
But the extremists hadn't counted on the boys' strength of mind, deep-rooted sense of right and wrong - or love for their families.
"The fighters hoped to create their own personal army of mini-terrorists from the boys whose fathers they had murdered for being non-believers."
Taha's ordeal began when ISIS took over his school in Kocho village, in the Sinjar Mountains, northern Iraq.
They ransacked the village and lined up Yazidi men and women in separate lines.The men were taken to the outskirts of the village, made to lay on the floor and shot.
'I was separated from my father. I do not know if he is alive or dead,' he said.
The women were transported to ISIS-held Mosul and sold off at a people trafficking market to be used as soldiers' sex slaves.
Meanwhile Taha was moved to a school in the Solag area, while ISIS rounded up all the Yazidi boys aged between seven and 15. From there they sent them to special training camp in Tala-Afar.
The fighters hoped to create their own personal army of mini-terrorists from the boys whose fathers they had murdered for being non-believers.
"'They told us we want to make an army to open Rome…[and] we will control the West and America,' Taha said."
But in order to do this they needed to brainwash them into their warped way of thinking.
In a mockery of an actual school day, the 200-or-so boys would sit down for lectures in “violent terrorism”, followed by practical weapons training.
The ultimate aim, the boys were told, was to conquer the so-called 'enemies of Islam'.
'They told us we want to make an army to open Rome…[and] we will control the West and America,' Taha said.
And all the time, the uniformed boys were reminded of their 'devil worshipping' past as Yazidi - and the fact their parents were now their enemy.
Taha recalled: 'They told us Yazidis are infidels and you don't have to go back to them…[and] if you find your parents and they have not converted to Islam, kill them.'
These lectures would be followed by practical lessons in how to fight, and use pistols, often held on the shooting range, on a field outside the crumbling school.
'We were terrified, and didn't want to use the weapons - but if we didn't, we would be beaten,' Taha said.
But there were other, far more disturbing lessons taught to the boys - some of whom were so young they would barely have left their mothers' sides before.
The boys were taught how to behead the 'infidels' in lessons which involved a student holding a 'blunt knife' while another enacted the role of his victim.
'They told us any infidel has to be beheaded,' he said - adding, 'It was so bad. What is the benefit of killing innocents? It was awful, scary. I was depressed, I didn't want to do these things. I cried.'
The boys had little strength to fight against the brainwashing attempts of their captors: there was only a short break for food each day - but it wasn't food anyone would be happy eating.
'We were given dirty food – rice and beans [and] sometimes soup, but it had worms in it,' Taha said.
Every moment, the boys were watched by at least two fighters, armed to the teeth.
But Taha and his friends still dreamed of escape, and were willing to risk their lives in order to be free once more.
In April - more than six months after they were first captured - that chance finally came, when Taha was allowed to visit his uncle's family, who lived on the outskirts of the city.
Sensing this might be their only opportunity, Taha and three members of his family fled.
'At night we ran away to Zumar into the safety of the Peshmerga,' he said.
Taha finally found safety in the Rwanga refugee camp in Dohuk, northern Iraq. His friends in the school have not been so lucky, and he is in little doubt of what the warped extremists have in store for them - to be used in the group's twisted fight against the world.
Some boys of Taha's age have been sent on suicide missions with bombs strapped around their waist.
'We did not get enough training, but they said in the future you will fight for jihad,' he added.