It was the first time the Tigers had beaten the Trojans since 1999, also with a last-minute field goal by the replacement kicker, although the two schools had only been reconfigured back into the same varsity competition - Tri-City Athletic League - this season, having last met in 2004.
The win took the Tigers to a 5-3 record so far this season, 1-2 in their league, and keeps them with a chance of making the playoffs with two games left.
Cornaga, who lives in the town of Lodi with his mother, was named "Athletic of the Week" by the local paper, the Lodi-News Sentinel.
He told the paper he kept his celebrations low key after the Friday night game.
"It was a pretty relaxing weekend," Cornaga said.
"I coached flag football for little kids, didn't do much else."
The teenager, who in the paper's profile said rugby is still his favourite game to play, had lived in the US in 2003-4 before moving back to his New Zealand father Mark Cornaga.
He always wanted to go to college (university) in America, so moved back to the States to live with his mother, Tamara Slatten.