It's a daft rule. I absolutly hate the idea. There is a difference between children running, yelling, shoving each other, being horrible to each other in the corridors and normal everyday conversations like
Child A "Do you still want me to help you with the maths after school"
Child B "Ooh yes please. Meet you in the library "
A "Are you going to Guides after school, do you still want to my mum to pick you up?
B "Oh yes, thanks for reminding me"
A" Hey B, did you realise you left your PE bag in the canteen. Miss X has it for you "
" Oh thanks for telling me A. I wondered where it was"
And 1001 other perfectly normal everyday conversations that people should be able to have with one other when they are inbetween and enroute to another lesson.