Putting his knuckles to mine in greeting, he isn't self-conscious about his clothes: wool tassels and colourful string are wrapped on to his head; one of his friends has the skin of a bush cat hung around his neck. A third, also wearing tassels, has a broken mirror tied into his hair. These, they explain, protect them from bullets.
These schoolmates are soldiers. "I have killed some people, I shot them," explains one. "I killed two rebels and it felt good. I was happy to kill them because they are our enemies."
He has fought for two years as a member of his village'sdefence force, the Kamajors, a traditional hunting society which now keeps order in this area.
There has been war in Sierra Leone since 1991, when the civil fighting spilled over the border from Liberia. The rebels, the Revolutionary United Front (RUF), claimed to be fighting against the corruption of successive governments, but when they seized power in May 1997 they faced massive public opposition.
More than any other group, the Kamajors organised civil and military resistance to the RUF and made the intervention by Nigerian "peace-making" troops possible in March this year.
The country's deputy defence minister, Chief Hinga Norman, claims the "war is over, there's just some fighting to be done". But the war is not yet over, and with the dry season beginning, United Nations observers expect more fighting to occur: the rebels will be able to move more freely and will be out to pillage harvests. One central tactic of the rebels is to recruit by abducting children and forcing them to fight, carry ammunition and looted goods. Around 3,000 children are said to be living in the bush with the RUF, which is said to have up to 8,000 guerrillas.
A similar number of children fight with the civil defence forces and guard checkpoints. One former civil defence soldier says that "at the battlefront it is children fighting children".
As a generation grows up more familiar with the workings of an AK47 or G3 assault rifle than with a classroom, many fear that the problems in Sierra Leone are set to last for many years. "A generation of children is stunted and traumatised," says Anthony Bloomberg, a representative of Unicef, the UN children's organisation, pointing to poor nutrition and education levels which already existed before the war. Now there is the added challenge of trying to reintegrate former child soldiers back into civilian life: sometimes back into villages which they are known to have attacked.
In schools near Bo former child fighters are being taught about childhood again, and are given carpentry, craft and household skills as well as foster families to ease their way to a new way of life. But they have to come a long way.
Many children in their mid-teens have been soldiers for half their lives: they have committed atrocities, killed, and suffered the deaths of friends and relatives.
One former administrator with the rebels was abducted with 28 of her family. "Only nine of us lived. The others died of illness or hunger while we were in the bush," she said. Children as young as eight months old have had limbs amputated, as a "message for President [Ahmad Tejan] Kabbah" - the elected President who was restored to power by the intervention force last spring.
The rebels appear to have no goals or ideology, other than to control the diamond-rich areas in the north and east of the country. There is talk of reopening negotiations: trying to find a way to persuade guerrilla fighters to leave the bush. But since the execution last month of 24 captured military leaders who were involved in the 1997 coup, the rebels in the bush may be less keen to talk.
The mess likely to continue, say aid workers and observers on the ground. And children will continue to be recruited "because we are braver than elder people", as one explains. "When we go to battle, the adults think of their wives and children. We don't think of them: we accept any order. I know I might be killed, but I feel secure."
He plays with the wool tassels in his hair. A 10-year-old friend then tells of the broken mirror: "If I point this at a rebel you will never see him again." Just the sort of thing 10-year-olds say all over the world, but this one carries an AK47.