We used to sing it at school. It begins:
Hail Glorious St. Patrick, dear Saint of our isle
On us thy poor children bestow a sweet smile...
and so on, then the chorus goes:
On Erin's Green Valley, on Erin's Green Valley...
etc, but I think there may be more than just one verse and the chorus.
It's quite well known, I think, so I'm sure lot's of you can help!