Children should no longer be "wrapped up in cotton wool" by their teachers.
Clive Davies, Wales spokesperson for the Forestry Commission, hit out this week at the zero-risk culture that he claims has emerged in Britain's schools.
Mr Davies spoke out as an English head, who banned her pupils from playing soccer in the school playground, was condemned in Wales.
Cathy Long, from Buckinghamshire's Burnham grammar school, slapped on a two-week ban after a teacher was hit by a ball.
Increasing threats of legal action over the past 10 years has led to many teachers refusing to take children on school trips.
But, at a conference held by the Commission this week in Carmarthen's Trinity College, teachers and parents were urged to let their children off the leash more.
Mr Davies said: "We want kids to be allowed to rekindle their interest in the natural world and to get out there and play."
The Commission has created spaces in its woodlands across Wales for children to play in and take "measured risks", and has teamed up with schools to create outdoor learning areas.
Soccer has also been top of the agenda this week as a new report called for the Football Association of Wales (FAW) to develop teacher-led centres of excellence.
There has been increasing frustration over the poor performance of Wales's national team, amid claims that the most talented young players are being poached by teams with more money and status over the border.
The report, by a cross-party committee of Assembly members, said local authorities should fund the release of teachers from the classroom to accompany teams to matches.
It also said the role of schools, local authorities and the FAW in raising the Welsh game should be more clearly defined.
Former Cardiff City FC player Garry Williams, now head of Merthyr Tydfil's Gwaunfarren primary school, already coaches young players, cherry-picking the best for his former club's youth academy.
He said: "We feel we have an obligation to provide children with the chance to play outdoors because so many of them never do that anymore."
Rhys Williams, campaigns officer for the National Union of Teachers Cymru, said schools needed to increase participation in all sports, and for all pupils.
He said more girls should be encouraged to take part in football and argued that the best players should be approached by outside organisations.
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