Early 1973, some 20 prominent Kenyans from Kiambaa Division led by the then Permanent Secretary for Education, the late Mr. Peter J. Gachathi, met and mooted the idea of building a secondary school for girls to give them better education opportunities. They had noted with a lot of concern that the girls from this area who missed a chance in National and Provincial Schools needed a pure girls school in Kiambaa Division.
The leaders decided to have it named in memory of the late Senior Chief Koinange wa Mbiyu, a great Kenyan who had played a unique role in the history of this country as a distinguished courageous leader of enormous imagination, courage, foresight and dedication to the advancement of Kenyans; a man who had established himself as a leading spokesman of the African People and had suffered detention for 8 years for his struggle in trying to liberate his people politically, socially and economically. He had also great love of Education for Kenyan people. His first-born, then a Minister of State, the late Hon. Mbiyu Koinange, another son Mr. Charles Karuga Koinange and another member of the family the late Gataa Koinange agreed to donate the land on which the first buildings were constructed.
- 1st meeting of 20 elders was held. An impromptu Funds Raising raised Kshs. 42,000/=.
- 4th February, 1973: First harambee meeting held. Kshs. 100,000/= was raised and it was used to put up initial classrooms.
- 15th February, 1974: The first 300 students were admitted (Form 1, 2, and 3).
- 3rd March 1974: The late Mzee Jomo Kenyatta laid foundation stone and raised Kshs. 350,000/= which was used to build more classrooms, two laboratories Dining Hall). Mama Ngina Kenyatta also raised Shs 1.3 million which was used to build 2 double-storey dormitories.
- August 1979: Share of Kshs. 265,000 raised by H.E. President Daniel Arab Moi for all Secondary schools in Kiambaa. The money was used to put up laboratory block.
- 1979: Government took over two day-classes – one for girls and one for boys.
- 1980: Government took over one girls’ Boarding class.
- 1983: H.E. President Daniel Arab Moi EGH, M.P. raised Kshs. 1.2 million. The money was used to put up a flat of 6 staff houses.
- 1983: Kiambaa Boys Secondary School was merged with Ex. Senior Chief Koinange Memorial Girls High School.
- 1986: H.E. President Daniel Arab Moi EGH, M.P. raised Kshs. 2.5 million. The money was used to build 4 classrooms, an ablution block for girls and a library block.
- 1987: Government took over 2 more government classes as a directive from H.E. the President.
- 1989: Built a Girls dormitory.
- 2000: Built a modern girls dormitory
- 2007: Made the school a single sex institution (Girls).