Often, a school has radically different requirements than a parish, even though the two are, physically, attached to each other. Schools have teachers, classrooms, assignments, etc., and serve a very different audience than a general parish.
Because of this, some schools have entirely different websites than their parent parishes, or, sometimes, the school has a unique section on the main parish website.
Whatever the case, here is a great site to get you started in your development of a website, social media solutions, etc.: