Bangor can consider themselves rather fortunate to have defeated Belfast High to earn a second round tie at home to Wellington College.
A try three minutes from time allowed them to progress but the visitors missed a late penalty to clinch victory.
The wind dominated the proceedings but both teams played better while facing it.
Bangor played their best rugby in the first period yet turned round 3-6 in arrears.
Both teams gave away far too many penalties and this disrupted the flow. Alex Bell kicked two for High and Stuart McCluskey replied for Bangor.
In the second period Bell increased the visitors’ advantage before a try was disallowed. McCluskey then converted another penalty to make the score 6-9.
In the fourth quarter, Bangor started to gain the upper hand and the visiting defence was put under extreme pressure.
When it looked as though High were going to hold out the home side scored the decisive try.
It was the only time that they had used their backs and it paid dividends. Four players were involved before Craig Harper touched down.
The High School were not finished yet. They took play down to their opponent's half where they were awarded a penalty. The long difficult kick into the wind was missed so Bangor survived.
David Kennedy, the Bangor coach, agreed that his team were a little fortunate.
“We started off well, dominating the scrums but then started to drift. We can certainly play a lot better than this,” he said.
Opposite number Kieran Doyle was disappointed: “We dominated large parts of the second half for no reward. I don't think we deserved to be beaten, but that's Cup rugby,” he said.
Bangor Grammar: J.Tugneri, P.Anderson, M.Aspley, J.Henly, C.Harper, B.Coulter, S.McCluskey, K.Harmson, T.Hagen, W.McGaughey, J.Wright, B.Galvin, D.Kelly, K.Lamont, G.Irvine.
Belfast High School: P.Brown, M.Boyd, R.McClean, P.Green, G.Stevenson, A.Bell, R.Creighton, C.Allen, G.McKeown, A.Gibney, R.McKay, R.Megarry, J.Whitley, H.Green, N.Duggan.