Many thanks to @rgan0 for sharing on twitter!
He has tweeted that John WIck is filming next door to the Flatiron School. Google is showing that the school is located in the Flatiron district but the school’s website gives an address down in the financial district.
I’m not familiar with the the school or the city. If anyone can shed light on it, please leave a comment.
Update: The Flatiron School used to be located on W 26th in the Flatiron district but has moved to 11 Broadway. Thanks Elaine!