Spencer, 18, the son of 35 Test All Blacks five-eighths Carlos Spencer, was fullback and goal-kicker for the Hamilton Boys' High School team that won the World Schools Festival Championship – an unofficial schools' world championship – in Thailand last month by beating South African powerhouse Grey College in the final.
Then, at the weekend, he stepped onto the world Sevens stage when making an impressive debut with the All Blacks Sevens, who won the Sydney leg of the HSBC World Sevens series.
He told rugby.com.au, "Three weeks ago I would not have thought I'd be getting my debut and flying to Sydney. To not only do that, but get the win, it's surreal."
Marking his first game, against Uruguay, with two tries, he also provided a try-assist in the 45-7 win.
He scored in the semifinal win over France and made some strong runs in the latter stages of the 38-0 win over South Africa in Sunday's final.
It was New Zealand's first win of the series after two runners-up medals in the preceding tournaments.
"I think we just kept it a little more simple.
"Sometimes we try and do too much, and [there's] also the hurt of losing. It's not easy losing two finals in a row, and we didn't want to make it three.
"All the boys played as a team and dug it out to get the win."
Getting the win, and extending their lead in the standings to nine points over South Africa, was a confidence boost for the side.
"We know that we can win, that's not new, but the confidence is now over the moon.
"Hopefully, we can keep that going into Los Angeles and, hopefully, I get the chance to go to LA and just keep working hard and see what happens."