The way has been cleared for Educate Together to build a school on the site of the former Harcourt Terrace Garda Station.
Dublin City Council had given permission to build the school for 700 pupils but that was appealed to An Bord Pleanála.
Some local residents had objected over traffic and congestion concerns. They didn't believe the Department of Education's estimate that just under half of students would travel there on foot.
An inspector for the planning authority agreed that the travel plans were unrealistic, but that was overturned by the board of An Bord Pleanála.
