Yes a child can go to school with slapped cheek syndrome.
Once the child has the rash of the slapped cheek syndrome the child is no longer contagious and cannot spread the slapped cheek syndrome to other kids around them.
The child's slapped cheek syndrome can only be spread during the week before the rash begins.
Once the rash of the slapped cheek syndrome appears the child cannot spread it to anyone else.
So after the rash appears on the child from the slapped cheek syndrome they can return to school, go to daycare etc.
The child is only contagious before the rash appears.