13 yr old DS - fleeting friendships, is this normal?

[PosiePootlePerkins]

Just after some perspective and advice please. 13 yr old DS seems to be going through a stage of having very fleeting friendships. He had a good solid friendship group through Junior School but since starting Senior School his friends seem to have drifted away. He'll talk about a friend, or couple of friends, I'll maybe suggest they get together out of school, then he's talking about different boys. He is definitely happy and settled at school, I don't think he's on his own at lunch etc, no other issues other than the normal teenage moods, but I just worry that he has lost those solid friendships he once had.
As a family do value our quiet time, I guess we lead a fairly quiet life at home, I wonder if DS is somehow missing out.
He does a self defence class twice a week and is very sociable when there, he loves going to it.
Is this normal? Can/should I do anything to help him? Sorry for rambling, just needed to get it out.

My experience with both DC is that year 7 they tend to stick more or less with the friends they had from primary as they settle in. Year 8 is a lot more fluid as they start to move around friendship groups. Year 9 some groups settle but others are still trying to find their place in the social scene. Year 10 they are pretty much settled and don't move around so much but do acquire new additions or a couple of cliques join together for a while. Year 11 is pretty stable and then they all go their separate ways for 6th form, college etc.

Thank you for your reply Angelicinnocent I really appreciate it. That actually makes an awful lot of sense and has put my mind at rest. And very helpful to know that it may continue! Always something to worry about, although I think its much more of an issue for me than him, so I'm trying hard to keep quiet!

That has been the case for DD. I thought it was just girls, but according to her boyfriend it happens to boys as well.

Thank you astonished that is reassuring. Senior school parenting is hard! Wish there was a handbook somewhere...

I agree. I found the primary school years much easier. I think social media doesn't help either.