Goals from Liam Trotter and Aidan Collins took Town into their first FA Youth Cup final for 30 years. The Blues, two-up from the first leg, went behind on the night when Simon Dawkins netted in the 63rd minute but hit back immediately though Trotter, Collins sealing the 4-1 aggregate win late on.
Bryan Klug and his staff picked the same side which won the Portman Road leg 2-0 last Friday. The Blues had the best of the early stages without creating any serious chances.
The first threat on either goal came in the 19th minute when Aidan Collins headed a deep Liam Craig freekick from the left into keeper Tommy Forecast's arms.
Chances continued to be rare but with Town having the better of it in midfield. On 35 Billy Clarke was fouled not far outside the area and, after being teed-up by Owen Garvan and Liam Craig, Cathal Lordan curled a shot just wide of the post.
Town ought to have gone ahead in the 44th minute when Liam Trotter was threaded through beyond the Spurs defence inside the area. However, a defender got back to muscle him out and played the ball back to the goalkeeper for what appeared to be a backpass.
Spurs had to wait until the last minute of the half to test Shane Supple in the Town goal. Andy Barcham crossed from the left and Charlie Daniels headed straight to the keeper.
Just before the whistle, Clarke and Knights exchanged passes but the England U17 international's cross was just too strong for Lordan coming in from the right.
Town had deservedly held on to their lead during the first period and might even have increased it. Spurs had rarely looked at all threatening and unsurprisingly made changes at the break, Jamie Davis and Simon Dawkins replacing Chris Riley and Radwan Hamed.
But it was Town who would make the early second half running and within a minute Liam Trotter had shot over the bar from the edge of the area after a Liam Craig cross from the left had been headed out.
From the corner, Garvan headed Craig's deep cross goalwards, a Spurs defender blocking on the line.
The home side had come out after the break with far more attacking endeavour than they had shown in the previous three halves of the tie. On 50 sub Dawkins broke quickly, held off Collins and hit a shot from inside the area which failed to seriously trouble Supple.
Tottenham's half-time changes opened up what had been a tight game in the first half and the Blues almost increased their aggregate lead when Lordan crossed dangerously from the right, a defender's foot just intervening ahead of Knights.
Craig sent in the resultant corner, Collins heading over off a defender. From the next corner, the ball eventually fell at the feet of Liam Trotter in the six-yard box but the midfielder couldn't direct it towards goal.
Spurs lost their captain, full-back Phil Ifil, in the 57th minute, Claude Seanla taking over and joining the attack.
Immediately Seanla was in the thick of the action, running through one-on-one with Supple from Stuart Lewis's pass. The Irish keeper stood up and blocked the sub's shot, Dawkins following up sent the rebound wide off Aidan Collins.
The home side went ahead in the 63rd minute. A Lewis corner came in from the left, Leigh Mills headed on at the near post and Dawkins nodded home.
Town hit back within a minute. A corner was cleared to 10 yards outside the area, Garvan looped it back over the Spurs defenders as they pushed out, Trotter took the ball down and classily slipped past keeper Forecast before languidly sliding it into the empty net.
Soon after the goal Town full-back Sammy Moore suffered a nasty injury when he collided with a post when trying to cut out a cross from the right. After lengthy treatment he was replaced with James Krause. A minute later Danny Haynes took over from Cathal Lordan.
Town came close to another goal in the 75th minute when a fine move down the left ended with Clarke crossing for Knights whose shot was blocked.
Spurs should have scored their second goal of the tie in the 81st minute when Seanla broke away beyond the Town defence. Shane Supple sent him wide and the sub shot wildly over the bar from a tight angle.
With three minutes remaining, Billy Clarke was fouled on the byline, a leg injury forcing him to be subbed. Liam Craig whipped over the freekick and Aidan Collins headed into the roof of the net to seal Town's place in the final.
The Blues threatened for the final time via Craig's freekick in the last minute but keeper Forecast held on with little trouble.
A thoroughly deserved win from the youngsters, perhaps not always as fluent a display as in the home leg or in the previous rounds against Aston Villa and Colchester.
Liam Trotter was probably the pick of the Town players, taking his goals with great confidence, while Craig was a big threat down the left.
Spurs were only dangerous once they had made their changes at the break and over the 180 minutes the Blues were a significantly better side.
Town: Supple, Moore (Krause 67), Synnott, Trotter, Collins, Casement, Lordan (Haynes 68), Knights, Clarke (Sheringham 87), Garvan, Craig. Unused: Reynolds, Haverson.