It was founded in 1865 by Theodore Leighton Pennell (11 March 1867 – 23 December 1912), an English Protestant missionary and doctor, as Bannu Mission School.

Wigram became the Principal in 1912 and after Dr. Pennell, much of the credit for raising the school to a high level efficiency and usefulness goes to him.

The staff left during partition, but Mr. Christopher, kept the school going until Principal Victor S. Joseph took it over from him in 1952 for thirty years.

Mano Rumalshah, Bishop of Peshawar, a decision was made to reconstruct the school building and to change the medium of instruction from Urdu to English.

In March 2005, Pennell High School, English Medium, Bannu sent its first badge of boys and girls of Matric for SSC Board examination.

[3] The US drone attack took place on 19 & 20 November 2008 and the Taliban, in retaliation, hit the Bannu district with 16 missiles.

[4] One January 27, 2015 hundreds of students protesting against a French magazine for publishing blasphemous cartoons of Muhammad stormed this school demanding its closure.