Green Party campaigners believe there is "overwhelmingly strong" evidence that the reduced limit is needed.
They want Shropshire Council to follow the example of Lancashire County Council, which has introduced a general 20mph limit on all residential roads.
It comes after calls to Shirehall for a 20mph limit outside Highley Primary School fell on deaf ears – despite youngsters at the school gathering a petition with 500 signatures in favour of the move.
The Green Party has pointed to research by the Local Government Information Unit, which shows pedestrians are seven times more likely to survive if hit by a car travelling at 20mph than if they were hit by a car at 30mph.
John Whitelegg, press officer for South Shropshire Green Party, said there had been a "substantial" fall in deaths and serious injuries in Lancashire since its new policy had been brought in.
He said: "Shropshire Council's decision to impose a seven times higher risk of death upon the schoolchildren of Highley is a betrayal of both its public health duty and common sense.
"We call on the council to reverse this decision immediately, to introduce a 20mph speed limit in the vicinity of every school in Shropshire, and to follow the example of Lancashire County Council and introduce a general 20mph limit on every residential road."