Latu Vaeno ran 50m with the ball, evading his opponents to go between the posts. Rotorua ran out 27-23 winners.
"With two minutes to go and eight points to collect the easy situation is to count yourself out," Buckton said.
"The principal's heart was stopping, but we've got used to these scenarios but it takes a lot of resolve and belief to stay on it.
"We're proud of the boys and having that belief.
"Our key momentum is about mental toughness, but it's not an easy thing to do with 17-year-olds."
Rotorua travel away to Napier Boys' High School next weekend. Rotorua are currently fourth in the table and Napier seventh.