Our young Reds raced into a two-goal lead during the first 45 minutes and went ahead when Ashton Missin fired past Shea Connor, finishing a slick team move in the process.
United then scored a second just four minutes before the break, with Charlie McNeill's low cross into the area tapped into his own net by Jack Hannah.
Middlesbrough pulled a goal back in first-half stoppage time, as Sonny Finch latched onto a mistake at the back to curl past Elyh Harrison.
The visitors completed their comeback through Finch and then Ajay Matthews in the second period, with the latter scoring just six minutes before the final whistle.