We had that exact situation in my DD's friendship group. It was such a nervous wait for that particular mum as there was about a 6 hour gap between results - passing Kent but not Shepway is quite unusual. Thankfully the children were all blissfully unaware as they were off on a residential with no contact possible!
Shepway results for us were through the Applicaa system - the results came online quite a while before the email notification arrived, so my obsessive webpage refreshing was vindicated!
And yes, the school will know and will not give you any indication at all. It was very odd knowing that they knew and we didn't. I think it was only the Head and Deputy that knew, class teachers weren't informed until the results were officially released.