Padbury C of E School has been granted full primary school status by Bucks County Council.
The school, which currently only takes children up to Year 4, will open its doors to Years 5 and 6 pupils from September.
The move to expand the school began last autumn with a formal consultation process, and the final permissions were granted during the Easter holidays.
Construction of a new classroom building for September will begin this term.
Headteacher Karen Duckworth said: “This is a really exciting development for the school and great news for local parents who want to keep their children at the same school right through to the end of Key Stage 2.”
At the start of this term, Padbury Pre-school opened the doors of its new building in the grounds of the school.