Northampton School for Boys will head to Allianz Park on March 3 as their bid to make it to Twickenham continues to take shape.
NSB beat The Judd School in the National Under 18 Cup quarter-finals on Wednesday, winning 19-3 against the Kent outfit.
And they will now meet Queen Elizabeths GS Wakefield as the two teams do battle for a place in the Twickenham final.
In Wednesday's last-eight tie, Judd had gone ahead thanks to an early penalty, but NSB were technically superb at the breakdown, lighting fast, abrasive and totally committed.
A line-break from Jake Johnson created a switch move, with winger Josh Lack driving over the line for NSB's first score.
A ferocious battle in midfield ensued but 10 minutes later, Ben McDonald broke from a scrum and fed No.9 Sam Connor, who used his acceleration to get in behind Judd and give the scoring pass to Lack.
Tyler Mills added the conversion to make it 12-3 at half-time against the wind.
The second half saw Ollie Sleightholme, son of former Saints and England player Jon Sleightholme, collect a kick and burst through several tackles for a wonderful individual try.
The conversion was again added by Mills, and NSB then showed real bravery in defence to see the game out for the final 20 minutes.
NSB coach Mark Lee was delighted with his team's display.
He said: "It was a fantastic performance from our boys against a very big side.
"Our bravery, commitment and desire were first class. Not one player took a backward step and it was our awesome defence that finally won us the game, although we also have some X factor in the backs.
"This is a very good group of players. They have played 15 and won 15 this season and are top of the English Schools Under 18 Performance League.
"They are a credit to the school.
"They are developing each week, improving their decision making and game management.
"They show no fear - and we like that."