The Wales head coach was at Llandarcy on Wednesday to take in the clash between Neath Port Talbot College and Coleg Llandrillo.
In a game interrupted by driving rain and lightning, the two sides shared a 7-7 draw with Luke Davies and Tom Williams scoring a try apiece.
"The great thing about schoolboy rugby is it allows players to play at a high level," said Gatland.
"It can be a conveyer belt for Wales going forward into the future and looking ahead to the 2019 World Cup."
Neath Port Talbot hooker Davies had given the home side a 7-0 interval lead with fly half Dylan Francis converting his score. But Llandrillo fought back after half time, Williams ensuring the two sides ended the game level.
"There was a real high standard of play and the good thing is there were some great athletes out there," Gatland added.
"They will only develop and hopefully achieve higher honours in the future. New Zealand schoolboy rugby is strong and has plenty of history and this is a new league which has been going for a short period of time.
"But if we can build on it and bring some good players through, it will be vital in developing the game in Wales. I'm hugely passionate about schoolboy rugby and if the regions get behind it, it will grow and grow. Good competitions produce good players and good coaches and I'm 100 per cent behind it."
Max Howells, Director of Rugby at Neath Port Talbot College, said: "I'm disappointed as when you play at home, you expect to win.
"But a draw was probably a fair result, it was a real tough battle up front. Llandrillo kicked us into the corners well and kept us in our own 22. We had the chance to win it at the end but it wasn't to be this time."
Elsewhere, Coleg Y Cymoedd pulled further clear at the top of the table with an 80-7 demolition of Bridgend College at Taffs Well while Coleg Gwent heaped more misery on Coleg Sir Gar with a 14-10 away win over the west Wales outfit.
In the Trophy competition, there was another win for Cowbridge Comprehensive, this time over Newport High School and Pembrokeshire Schools registered their first losing bonus point in a narrow 24-18 defeat to Llandovery College.
WRU Wednesday League results:
Neath Port Talbot College 7-7 Coleg Llandrillo
Coley Y Cymoedd 80-7 Bridgend College
Coleg Sir Gar 10-14 Coleg Gwent
Cowbridge Comprehensive 29-12 Newport High School
Pembrokeshire Schools 18-24 Llandovery College