"It was disappointing after leading 2-1 at half-time but we just didn't defend in the second half and we were punished for it," the under-18 coach Hughie McAuley told the club's offical website.
"Marvin scored two good goals and we played quite well in the first half, but in the second half Middlesbrough took advantage of our inexperience at the back. There is still a lot of hard work to be done on the training ground with the lads."