You do need to address the rudeness - it gets very ugly indeed as they get older and won't necessarily go way on its own.
I have taught in a secondary school for 12 years and have definitely noticed that there are more and more pupils who can't just accept it and 'own' it when they have done wrong - instead they argue and justify. This thread has hit a nerve with me because, as HoD I deal with a lot of behavioural issues and I have spent about 4 hours this week on that. This is in exam season when I have pupils coming back for revision every night. It's an appalling waste of time and impacts on others.
These kids can't just mumble "sorry miss," and go on their way like they used to. Now it's "I was just..." "It's only a drink..." "But I've done the work..." "It wasn't me..." "Everyone else was..." Forever. No moment of acceptance ever dawns. Issues are unresolved.
I have spoken to a couple of parents this week as well. One boy had written a 3 line sentence instead of 5 paragraphs and refused to accept he hadn't done the task as "I've done it in one."
. He walked away from me in detention. His mother said "Oh yes, if he believes he's in the right he will just walk off. He's so honest with a real sense of justice." Great.
I wonder what is going to happen to these kids when they leave school and just can't be told anything, ever. I'm not a rubbish teacher, by the way, and this stuff wastes everyone's time and is certainly one of the reasons why so many people leave teaching after a few years. No wonder the teacher you spoke to wasn't cheery.
OP, I'm not saying your son is like this or that you would continue to make excuses for him throughout school, but these kids at my school did not suddenly become like this at 12 after years of being compliant and polite. Seven is not too young to start addressing this and it will be harder the longer you leave it.
My ds (10) is pretty logical and well-informed and sometimes says he knows everything/is a genius (to me - don't think he's ever said it to another adult). I have said, when he goes too far, "Do you honestly think you know more than someone 30 years older than you?" (He does, about cricket for example, but if it's about another topic and he's being annoying I pull him up) and he sees the logic of that. We also talk about one of his heroes, David Attenborough, and how he clearly doesn't think he knows it all and is trying to find out more. No one likes a know all.