A central school was a selective secondary education school in the English education system, between the more prestigious grammar schools and the ordinary secondary schools.
Central schools were established throughout the country following the Education Act 1918, although London County Council had established them in 1911 and ran fifty by 1918.
Following the Education Act 1944, the selection process was changed so that those who failed the eleven plus exam, but were considered clever enough to have been entered for it, were able to go to central schools.
References
Central school Wikipedia(Text) CC BY-SA