Jamhuri High School in the Kenyan capital had to be closed down for five days after the huge brawl broke out.
Tensions were said to have been high at the 1,400-pupil school for weeks after pupils of both religions claimed they were being discriminated against.
The boarding school came under fire for designating separate bathrooms and sections of the library for the two faiths, Morning Star News reported.
After a number of Muslim students tried to force Christian boys to recite the Koran, an enormous brawl broke out.
Youngsters were attacked with crude weapons including machetes, clubs and rocks as the violence raged.
A witness told the paper: “Some Muslim students forcefully tried to induct Christian students into their Islam faith, and those who refused were knifed, while others were physically beaten.
“The knives and machetes used are alleged to have come from outside the school.”
Up to 35 students of both religions were left wounded, with seven treated for stab wounds.
Jamhuri High School Principal Fred Awuor also needed hospital treatment after he was hurt in the chaotic scenes.
Authorities temporarily shut the school down following the January 23 fight.
They are now investigating how the weapons were smuggled into the school building.
