The Reds took the lead midway through the first half thanks to in-form forward John Cofie, who scored his fourth goal in as many games for the Academy side. Cofie latched onto an Etzaz Hussain through-ball before keeping his cool to out-muscle his marker, round the Middlesbrough goalkeeper and roll the ball into the net.
Ryan Brobbel almost drew the visitors level just before the break, but his shot was tipped onto the crossbar by United custodian Liam Jacob. From the resulting corner, however, Brobbel clipped a neat finish into the far corner from just inside the penalty area.
That's how the score remained, although the visitors missed a late chance to take all three points when Curtis Edwards saw his close-range shot saved.
The result leaves United – still yet to lose in 2010/11 – with 10 points from four games.