The light of understanding flickered in one lad's eye: "Oh, right," he said. "Like the Barlinnie Wall?" While it's true that there is only a few letters difference between Berlin and Barlinnie and, at speed from the M8, the perimeter fence of Her Majesty's Prison is faintly reminiscent of Checkpoint Charlie, his response reminded me once again that every individual pupil brings a different perspective to what he or she hears and does in school.
Unfortunately, we sometimes seem to be living in a world that views many things, including schoolchildren, from a perspective that can best be described as tabloid. How else can we explain media reaction whenever a schoolchild is in the news. Girls are always "angels", "quiet and studious" or "wild"; boys are "responsible", "sports mad" or "from a troubled background".
While appreciating the need for journalistic copy, often with the minimum of genuine detail available, it surely must bring additional heartache to bereaved parents to see their loved ones reduced to a collection of cliches. Any parent or teacher will avow that it is the very fact that children cannot be stereotyped in such a way that makes each of them so special.
Most young people have strengths and weaknesses, good and bad points, and those who know them celebrate the fact rather than seek to categorise them into a neat box.
To be fair, it's not just in the media that this homogenisation takes place. Shops near schools regularly sport signs declaring, "No more than two school pupils will be served at any time", thus tarring whole school populations with the same potential-shoplifter brush, and members of the older chattering classes, with time on their hands, always feel well able to comment on "young people today" by virtue of a bad moment at a bus-stop.
It is easy, too, for teachers to slip into a similar way of thinking "Third year are a bad lot" or "4X are always trouble" without stopping to consider the effects of constantly negative expectations.
Ever since teenagers were invented by a post-war market anxious to tap into their spending power, it has been an uphill struggle for school pupils to retain their individuality in the eyes of the "outside world"; they surely deserve more respect from those they encounter in school.
Looking for the good in every pupil may be a hard struggle from time to time, but failing to give pupils the opportunity to display their more positive attributes must count as a serious dereliction of educational duty.
Not for the first time, I am reminded of Professor Ripaldi's lines: "When we adults think of children, there is a simple truth which we ignore: childhood is not a preparation for life, childhood is life. A child isn't getting ready to live, a child is living."
It would be a major step forward if we could remember that more often, in all areas of life, and stop building all those Barlinnie walls to limit and contain children within our own misconceptions.