20mph limits outside schools is a good thing, due to large numbers of people coming and going and especially for children or where there are high volumes of pedestrians and cyclists. A 20mph speed limit signals to drivers to slow down and take care. But we should not limit the benefits of 20mph limits to outside the school’s entrance.
Traffic will already be travelling at less than 20mph outside schools at busy times due to the number of people arriving or leaving, along with the volume of traffic and parked cars etc. To travel any faster than 20mph at these times would be wholly irresponsible. It is away from schools where people are making their way to the school, where the 20mph limits are most needed.
People need to be safe from the point where they leave their front door, to the point where the enter the school grounds and that means a far wider area than directly outside the school gates. Default 20mph limits are needed for their entire journey through residential areas.