perimeter fence

plural perimeter fences

1. A fence that circles the perimeter of an area in order to prevent access.

   1 more example

   So if your prospective school is proudly displaying that "We Are Outstanding" banner on its perimeter fence, well, that is wonderful … but do bear in mind that in all likelihood it has been awarded for results in those two subjects, rather than for its delivery of a broad and balanced curriculum which brings out the best in every child. Which is, of course, what makes a great primary school.

   2014 September 23, A teacher, “Choosing a primary school: a teacher's guide for parents”, in The Guardian