http://www.bbc.com/news/world-africa-29985252
http://thenewsnigeria.com.ng/2014/11/10/breaking-boko-haram-bombs-nigerian-school-many-students-feared-dead/
The explosion happened at a boys' science and technical school in the town.
Militant group Boko Haram is believed to have caused the blast, police said.
It has often targeted schools during its five-year campaign to establish an Islamic state, which has left thousands dead.
A suicide bomber disguised in a school uniform caused the explosion, survivors are quoted by Associated Press news agency as saying.
"We have 47 dead and 79 injured," police spokesman Emmanuel Ojukwu told AFP.
The school was a mass of abandoned footwear and blood, resident Adamu Alkassim said.
"The students had gathered for the morning assembly when something exploded in their midst with a thunderous sound at exactly 7:50 am [06:50 GMT],"
a sobbing teacher is quoted by AFP as saying.
Victims were being rushed to a nearby hospital, said the teacher, who asked not to be identified.