There was a school in Newry Street, just above 2nd Rathfriland Presby. Church. It may well have been the R.C. one, as the former National School was further up that road.
As for the graveyards, your best bet would be R.S.J Clarke's "Gravestone Inscriptions" which come in a plethora of volumes, none of which specifically mention Rathfriland, but cover the small, older graveyards in each district. You just have to look via townland names, but these cover both R.C. and Protestant graveyards.