كتب : Hatem Maher
Rejuvenated Julio Baptista scored the winner nine minutes before the break after a neat exchange with Ruud van Nistelrooy.
Schuster will be delighted to receive such a precious present as he won his first El Classico in charge of Real.
The defending champions are in charge of the league table with 41 points, seven ahead of second-placed Barca.
The visitors had the advantage in terms of possession early in the first-half as Barcelona were a little bit cautious.
Real had the first chance after 12 minutes when Pepe dived to connect with Wesley Sneijder's free-kick but his header went straight into the hands of Victor Valdes.
Barcelona pushed forward afterwards and threatened Los Merengues but superb goalie Iker Casillas was on alert to foil the Catalans' attempts.
In the 30th minute, Samuel Eto'o pounced on Pepe's loss of concentration to go clear but Casillas rushed out to block the Cameroonian's attempt.
The ball slipped to Andres Iniesta but the Spain guardian once again produced a moment of brilliance when his outstretched hands sent the ball away.
Barcelona should have been in front four minutes later, only to be thwarted by Casillas.
Iniesta outpaced Fabio Cannavaro down the right before providing a low cross to the unmarked Ronaldinho, whose shot from inside the area was blocked by the 26-year-old.
Brazilian versatile striker Baptista, whose career with Real was revived by Schuster, broke the deadlock against the run of play in the 36th minute.
A wonderful aerial give-and-go between Baptista and Van Nistelrooy released the former Sevilla man who hit a powerful right-footed strike into the top corner of the net.
Barcelona enjoyed plenty of possession in the second period but lacked the composure and quality to trouble Casillas. Attacking trio Ronaldinho, Eto'o and Deco failed to impress.
Real were dangerous on the counter as Robinho wasted a glorious opportunity in the 55th minute after a surging run in Barca area.
Barcelona coach Frank Rijkaard introduced Bojan instead of Xavi late in the game and the youngster made an impact shortly after.
His shot from the edge of the area was parried by Casillas six minutes from time.