Parkour enthusiasts taking part in their sport on a school building in St Neots have contributed to calls for a security fence nearly eight feet high to be built around is perimeter.
The green weldmesh fence, which includes gates and turnstiles, is also designed to reduce crime at Longsands College.
A bid to build the fence by the Astrea Academy Trust, which runs the school, has been approved by Huntingdonshire District Council.
The 2.4 metre fence had been given the thumbs up by St Neots Town Council which said it was "essential to ensure the safety of all site users" but the district council's own conservation officer said that although the school's own heritage statement referred to anti-social behaviour at the site, there was "no specific justification for the extent or the height" of the fencing proposed.
"This proposal fences in a wide area of existing open green space within the conservation area, particularly along Longsands Road and along Priory Hill Park, a long distance from the school," the officer's report said.
"This is considered harmful to the character of the conservation area without clear and convincing justification for the proposed extent of this fencing."
A separate report by a council officer said the school had complained that its buildings had been used for parkour, also known as free running, in which participants run and jump over objects, including buildings and other man-made structures.
The report said: "The applicant advises that they need the fences for the safety of school staff and pupils, to deter parkour on the buildings, vandalism and anti-social behaviour, trespass and disruption of lessons and exams.
"It is considered that the extent, height and design of the development as described above will inevitably alter the character of the site and its surroundings somewhat due to the lessening of the openness of the site.
"However, it is considered that the enclosures will not be unduly intrusive due to the set back position from the paths, with the proposed fences generally being behind existing hedges or replacing other similar fences.
Eight members of the public commented on the fence, including five objectors who said it would harm the appearance of the area, would create a "fortress/prison" like feeling for residents and that a two-metre structure would be more appropriate.
Two were in favour of the fence, saying it was similar to the one at Ernulf Academy and would help reduce vandalism and anti-social behaviour.
The police designing our crime officer said in his report: "There have been numerous incidents over recent years at this location in relation to anti-social behaviour, burglary into the premises, vehicle nuisance - cars being driven across the school grounds - and other criminal offences such as criminal damage and youths on the roof.
"The fencing being proposed is likely to have a reasonable effect on reducing these incidents, it is secure but still allows good surveillance which will help safeguard the pupils and staff with secure access-controlled gates."
The officer added: "In view of the above a height of two metres would be acceptable to retain the security and be less visually intrusive."