Pointless if it's not compulsory.
Many parents don't test their children as it is or don't isolate when they are ordered to for a variety of reasons. The main one being that they won't get paid if they don't work (don't get me started on the government's stance on this issue),.
One of the parents at our school actually sent her children into school despite the fact she had tested positive.
Obviously there will be children who cannot be tested for medical or SEN grounds. These children are known to school and could be exempt.
It's really not that difficult and "They might not like it," really doesn't cut it for NT children during a global pandemic. It's nothing that staff haven't been doing for months.