Extra county secondary schools in Nairobi county are grouped into three clusters; cluster one(C1), cluster two(C2) and cluster three (C3).
Aquinas high school, Ofafa Jericho, Buruburu Girls among other schools form cluster one schools.
| S/N | SCHOOL CODE | SCHOOL NAME | TYPE | CLUSTER |
| 20401001 | AQUINAS HIGH SCHOOL | Boys | C1 | |
| 20401005 | OFAFA JERICHO HIGH SCHOOL | Boys | C1 | |
| 20401007 | BURUBURU GIRLS SECONDARY | Girls | C1 | |
| 20403004 | NGARA GIRLS' HIGH SCHOOL | Girls | C1 | |
| 20405004 | PRECIOUS BLOOD RIRUTA | Girls | C1 | |
| 20405007 | NEMBU GIRLS HIGH SCHOOL | Girls | C1 | |
| 20406002 | STATEHOUSE GIRLS HIGH SCHOOL | Girls | C1 | |
| 20406011 | ST. GEORGE'S GIRLS' SECONDARY SCHOOL | Girls | C1 | |
| 20410001 | MOI GIRLS' SCHOOL NAIROBI | Girls | C1 | |
| 20410002 | UPPER HILL SCHOOL | Boys | C1 | |
| 20401002 | HIGHWAY SECONDARY SCHOOL | Boys | C2 | |
| 20401020 | ST ANNE'S GIRLS' SECONDARY SCHOOL | Girls | C2 | |
| 20405001 | DAGORETTI HIGH SCHOOL | Boys | C2 | |
| 20406009 | HOSPITAL HILL HIGH SCHOOL | Boys | C2 | |
| 20401003 | HURUMA GIRLS' HIGH SCHOOL | Girls | C3 | |
| 20401004 | OUR LADY OF MERCY SECONDARY SCHOOL SOUTH B | Girls | C3 | |
| 20402004 | UHURU SECONDARY SCHOOL | Boys | C3 | |
| 20406019 | HIGHRIDGE GIRLS BOARDING SECONDARY SCHOOL | Girls | C3 | |
| 20409002 | MUHURI MUCHIRI BOYS HIGH SCHOOL | Boys | C3 |