I think it was a seminary. I skimmed through some of this and there is mention
http://snap.waterfordcoco.ie/collections/ebooks/106550/106550.pdfI was going to suggest, as you have done, that this might have been the reason for the boys’ education there.
I knew several boys from our parish and schools (English) who were ‘recruited’ from church missions and primary schools perhaps, and then received their secondary school education in religious establishments. Some may have remained and gone on to seminaries but some left after their education.