Thompson-Dunn praised the input from the subs bench.
"Full credit to the bench. Making the top four is an honour and hopefully we can do it again," Thompson-Dunn said.
His team's defensive effort was superb. All of Palmy's points came from the boot of fullback Ruben Love who kicked five penalties from eight attempts at goal.
First five-eighth Latrell Ah Kiong was again outstanding in all aspects of play. His classy aerial skills were again highlighted when he collected a high ball and sent Tupou away for his third try in the 51st minute.
Fullback Mercedes Hodge was again enterprising and scored two clever tries. His first in the 44th minute, which was against the run of play, was the turning point in the game.
Scorers:
Hastings Boys' High School 45 (Mefi Tupou 3, Mercedes Hodge 2, Emil Crichton, Charlie Varcoe tries; Latrell Ah Kiong 3, Jordan Thompson-Dunn 2 cons), Palmerston North Boys' High School 15 (Ruben Love 5 penalties). HT: 17-15.
■ The Hawke's Bay Saracens were pipped 27-24 by Wellington Development at Porirua's Jerry Collins Stadium today.
Saracens manager Richard Kinnear said the Saracens, who trailed 17-12 at halftime, performed well as a team. Magpies squad members, hooker Jacob Devery and lock Elijah Martin, were both prominent and scored tries.
Blindside flanker Phil McRoberts again had a high workrate as did gutsy prop Jasper Wylie. Winger Anzelo Tuitavuki was thirsty for work.
Loosies Ricky Hayes and Iakopo Mapu provided quality impact off the subs bench. Tuitavuki and fullback Marty Watson scored the Saracens other tries and first five-eighth Johnny Lauano kicked two conversions.
In the curtainraiser the Hawke's Bay under-19s were walloped 50-7 by their Wellington counterparts. Bay manager Tim Jones said his troops were competitive in the first half and trailed 12-0 at halftime but were guilty of leaking some soft tries in the second half.
This loss means Hawke's Bay have missed out on the top eight section of the national tournament which begins in Taupo next weekend and they will compete in the Championship division. Lock Tiaki Fabish and blindside flanker Josh Gimblett were the pick of the Bay forwards.
Centre Gideon Kautai was the best of the Bay backs and scored the visitors only try which was converted by halfback Sam Walton-Sexton.