Playing with 100 players in the starting line-up, the school children comfortably bettered their professional counterparts in a match set up by sponsors McEwan Fraser Legal.
After the full-time whistle, Robertson was asked about his team’s performance, with the ICT boss admitting he got his tactics wrong.
He said: “We pride ourselves on our team shape and discipline, and today it just didn’t happen.
“I said to the players that when you’re defending you must show the players into the wide areas and we just allowed all 37 of their forwards to rush through the middle.
“It’s unacceptable. We have to get back on the training ground tomorrow and make sure it doesn’t happen again. I’m sorry, to concede 20 goals to any team is not on.
“I must admit, we had them watched. And we were sure they were going to play a 50-25-25 formation, but they didn’t, they played the opposite. They played a 30-30-40 and it caught us out.”