The school in Bannow was formerly an agricultural collage run by a Mr. Hickey and taken over by the Rev. Newlands and set up a type of secondary school named "...
Bannow grammar school, for the preparation of young men for the Irish University..." see :
Parish of Bannow (Samuel Lewis - Topographical Directory 1837)
So not a likely location for his engineering training. I believe the school was located in the townland of Kiltra to the west of the town of Carrick
links to two of the articles on James Crawford :
Cyclopedia entry for James Crawford Obituary - James Crawford (Papers Past)
The first is a transcription of an older item and mentions "
..born in Liverpool, and educated at Barrow, Wexford, Ireland.." It might be worth checking an original of this book to see if Barrow is a mistranscription .. or two separate places may have been mixed up (i.e. Barrow and Wexford)
The second article is from a newspaper of the time and makes no mention of Barrow or Bannow, just Wexford
The school of Engineering in Trinity was setup in 1841 and was one of the first Engineering Schools in the English speaking world. See :
http://www.tcd.ie/Engineering/Shane