If children have symptoms they should be sent home and get parents should then arrange their own child tested.
Teachers are not trained nor insured to swab numerous children, there are plenty that could go wrong without training and guidance.
I really feel for teachers across the UK right now who have worked incredibly hard to ensure schools are open and as safe as possible. Now their christmas holidays are being upheaved so they can arrange online learning, key worker systems, and swab testing systems. All at the drop of the hat.
Its another unrealistic idea that wont work and will continue the spread of the virus as people will refuse testing (rightfully so) it wont be possible for schools to maintain and boris will just go back to the drawing board.