The prestigious Park Avenue Day School officially split Friday from the Park Avenue Christian Church after it was forced to relocate from the Upper East Side, The Post has learned.

The split came after the church sold its five-story annex to real-estate developer Extell, forcing the nursery school to relocate. It moved to the Upper West Side before the current school year.

Under the separation agreement, the school keeps its assets and more than $1 million from the real-estate deal. It has renamed itself the Park Children’s Day School.

“We are so pleased to begin this new chapter for Park Children’s Day School,” said executive director Betsy Newell.

The school has signed a 10-year lease at the West 76th location and will continue operating as a nonprofit organization.