What is a County School? County schools in Kenya fall below extra-county schools in the national school ranking. There are hundreds of extra county schools in Kenya. County school institutions are part of the four-tier secondary school system in the country. This article lists the county schools in Nairobi county in no particular order.
Some of these schools are the best performing county schools in the Nairobi region.
| School Code | School Name | Category | Type | County |
| 20401006 | NILEROAD SECONDARY SCHOOL | County | Girls | Nairobi |
| 20401008 | MAKONGENI HIGH SCHOOL | County | Mixed | Nairobi |
| 20401021 | ST PATRICK NAIROBI MIXED SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20402001 | EASTLEIGH HIGH SCHOOL | County | Boys | Nairobi |
| 20402002 | ST. TERESA’S BOYS | County | Boys | Nairobi |
| 20402003 | MAINA WANJIGI SECONDARY SCHOOL | County | Girls | Nairobi |
| 20402005 | KAMUKUNJI SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20402006 | O.L.M SHAURI MOYO GIRLS SECONDARY SCHOOL | County | Girls | Nairobi |
| 20403001 | JAMHURI HIGH SCHOOL | County | Boys | Nairobi |
| 20403002 | DR. RIBEIRO PARKLANDS SCHOOL | County | Boys | Nairobi |
| 20403003 | PUMWANI SECONDARY SCHOOL | County | Boys | Nairobi |
| 20403024 | COUNTY GIRLS HIGH SCHOOL- NAIROBI | County | Girls | Nairobi |
| 20403025 | C.G.H.U. MIXED SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20403026 | PUMWANI GIRLS SECONDARY SCHOOL | County | Girls | Nairobi |
| 20404001 | LANG’ATA HIGH SCHOOL | County | Boys | Nairobi |
| 20404022 | KAREN ‘ C ‘ SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20404032 | LANGATA BARRACKS SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20405005 | MUTUINI HIGH SCHOOL | County | Boys | Nairobi |
| 20405006 | RUTHIMITU SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20405008 | RUTHIMITU GIRLS SECONDARY SCHOOL | County | Girls | Nairobi |
| 20405009 | DAGORETTI MIXED SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20405048 | BETH MUGO HIGH SCHOOL | County | Mixed | Nairobi |
| 20406001 | PARKLANDS ARYA GIRLS HIGH SCHOOL | County | Girls | Nairobi |
| 20406007 | KANGEMI HIGH SCHOOL | County | Boys | Nairobi |
| 20406012 | NAIROBI MILIMANI SECONDARY SCHOOL | County | Boys | Nairobi |
| 20406018 | LAVINGTON MIXED SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20407001 | OUR LADY OF FATIMA SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20407002 | KAHAWA GARRISON SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20407003 | RUARAKA HIGH SCHOOL | County | Mixed | Nairobi |
| 20407004 | KAMITI SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20407005 | BABA DOGO SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20407037 | KARIOBANGI NORTH GIRLS SECONDARY SCHOOL | County | Girls | Nairobi |
| 20407045 | NEW MWANGAZA MIXED HIGH SCHOOL | County | Mixed | Nairobi |
| 20407059 | GARDEN ESTATE SECONDARY | County | Mixed | Nairobi |
| 20407061 | MWIKI SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20407063 | HON JOHN NJOROGE SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20407065 | CLAY CITY SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20408001 | THE KOMAROCK SCHOOL | County | Mixed | Nairobi |
| 20408007 | EMBAKASI GIRLS SECONDARY SCHOOL | County | Girls | Nairobi |
| 20408014 | PETER KIBUKOSYA SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20408015 | KAYOLE SOUTH SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20408020 | MWANGAZA SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20408029 | EMBAKASI GARRISON SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20408042 | UTAWALA SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20409001 | DANDORA SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20409003 | HON. DR. MWENJE SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20409004 | USHIRIKA SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20409005 | JEHOVA JIRE SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20409006 | DRUMVALE SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20409007 | ST. GEORGE ATHI SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20409024 | RUAI GIRLS’ SECONDARY SCHOOL | County | Girls | Nairobi |
| 20409025 | RUAI BOYS SECONDARY SCHOOL | County | Boys | Nairobi |
| 20409026 | MIHANG’O SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20410003 | RAILA EDUCATIONAL CENTRE | County | Mixed | Nairobi |
| 20410004 | SHADRACK KIMALEL MIXED SECONDARY SCHOOL | County | Mixed | Nairobi |
| 20410005 | OLYMPIC HIGH SCHOOL | County | Mixed | Nairobi |
| 20411001 | ST TERESA’S GIRLS SECONDARY SCHOOL | County | Girls | Nairobi |
| 20411004 | NDURURUNO SECONDARY SCHOOL | County | Mixed | Nairobi |
All the county schools in Kenya admit students majorly from within the County they are located in. Admission of form ones is done through the Education Ministry’s Portal and the admission letters to these schools are downloaded from the Ministry’s website.