The day he was told off at school became a defining moment for renowned environmentalist Jonathon Porritt - because he was not a recalcitrant child, he was one of the teachers.
His crime had been to take a class of pupils at Burlington Danes comprehensive, west London, to sit beneath trees on the school grounds for their lesson. Mr Porritt was an English teacher and directed drama at the school from 1974-1984.
"I was in trouble," said Mr Porritt, an icon of the green movement, "because the grounds were there not to be used by anybody but to be admired from the school windows.
"I could see instinctively that was completely wrong. Kids were being asked to go through school without any opportunity to have contact with the natural world."
Speaking at the national school grounds charity Learning Through Landscapes (LTL) conference in London last week, Mr Porritt, a former government adviser on sustainable development, demanded that more be done to help all schoolchildren, including teenagers, learn outside.
There have been concerns that the pound;55 billion Building Schools for the Future programme is not paying enough attention to school grounds. Indeed, a report from Ofsted in 2008 also found that grounds were rarely considered as a resource for learning.
Mr Porritt, who is a patron of LTL, said that there was a lot of good practice going on and some fantastic examples, but it should be the norm across the new build programme.
"There is a palpable sense of disappointment," he said, "that many barriers have been put in the way of doing this: affordability, competing priorities, the fear that the landscape would not be respected by secondary students."
He said that it was clear from observing nursery children that they enjoyed being out exploring nature. "Mindsets are changing, young people are more attuned to the dynamics of living sustainably and we have to go on deepening that.
"We have to make it possible for young people to emerge from their educational experience imbued with the sense of connectedness to the natural world. That must be the start from day one, on their first experience in education, and continue all the way through."
Catherine Andrews, chief executive of LTL, told the conference: "What we are providing for children outside in the new build programme is not good enough. Outside space makes up 63 per cent of the school estate and it is shocking not to make use of that for young people's needs."
Meanwhile, attitudes have changed at Burlington Danes since Mr Porritt got himself in trouble. The school, now an academy, is made up of several buildings ranging from the Burlington Building - an example of art deco architecture - to a new wing with triple-height floor-to-ceiling windows. There are extensive fields and hard play areas - which include a space for all-weather table tennis and table football equipment. And no shortage of outdoor learning.
And this week, a new row of trees was planted.
pound;50K IMPROVEMENTS REAPED BENEFITS
A report on a research programme into improving secondary school grounds found there were benefits - but careful consultation was needed with students.
Six schools took part in the Grounds for Improvement Secondary Action Programme. They received pound;50,000 each to develop their grounds between 2001 and 2004.
The changes ranged from a basketball area, seating, trees, cycle racks, an activity equipment trail to a new garden with quiet social areas and a river-effect trail.
An evaluation by the National Foundation for Educational Research and Learning Through Landscapes found students taking part in the process had learned about collaboration, teamwork and compromising.
But students in three schools felt staff would not be willing to use the facilities for learning.
The report warned that benefits of improved attitudes and new resources could be scarce if students felt the developments were not what they asked for, did not meet their needs, were in the wrong place or would be vandalised.
For more ideas on outdoor learning activities visit the Outdoor Learning forum