“In the second half they showed their skill and blew us out of the water,” said Bradley.
GBHS bounced back with a 24-12 win over New Plymouth's Francis Douglas Memorial College.
They lost their next two games — 24-7 to Timaru Boys' High and 36-0 to De La Salle College of Auckland.
Bradley said the other teams in their pool were well-drilled and fit.
“Fitness-wise, they're up to it. It's just the mental fatigue of four games against top-level teams. That comes with experience of multiple tournaments.”
GBHS have not been to the national tournament in seven years.
They were back in action this morning against New Plymouth Boys' High School, who they beat several weeks ago at the Super-8 sevens.
Gisborne Girls' High get their campaign under way today.
They play Feilding High, Auckland Girls' Grammar, Hastings Girls' High and St Peter's College, Cambridge.
Coverage of the tournament is live on Sky or live-streaming through Sky Sport Next on Youtube.