The intensely creative and innovative developments in New York in the 1940s gave birth to the radical and world-conquering new style of painting that in the early 1950s became known as abstract expressionism. The two terms are effectively interchangeable, that is the artists of the New York school are the abstract expressionists.
The term New York school, which seems to have come into use in the 1940s, has echoes of school of Paris and may also be seen to reflect the notion that after the Second World War, New York took over from Paris as the world centre for innovation in modern art.