They are still your lovely boys inside, even when they are wrestling a bit with who they are in the world, and what their role is in that world
That (I'm no medic, but this is my experience) they seem to have growth spurts in a sudden burst - they don't mean to knock things over an bump into things, but they genuinely lose that sense of 'where they are in space' when they don't know how long their arms are
It is excruciatingly painful (figuratively, not literally) when your voice breaks and you have no idea how it is going to come out of your mouth - often just at a time when "sounding cool" really matters.
They almost certainly will disappear off to their rooms for a couple of years when you only tend to see them when they come out for food. This is a really good time to keep talking and to keep listening.
My top tip, if you are making a new start anyway, is to establish a routine now, if you don't already do it, of sitting down together to eat your evening meal together every day, and have conversations about everything and nothing. Not questioning them about their lives necessarily, but talking in general terms - about something in the news or about "X, at work was telling me that at her ds's school this is happening. I didn't realise people did that, is it commonplace?" or "Y (your mate) was saying that her niece was offered alcohol at a party and she didn't really know what to do. What would you do in that situation?"....... or "Z (neighbour) was telling me about this, that she saw on the bus last week. I don't know what I would have done in that situation." etc etc etc, so there is always lots of discussion and time to think about situations that might occur some time in the future, before they ever arise, and before it is personal and seemingly about them or their friends.
Encourage them to peruse an interest with other friends outside school - sport, drams, Scouts, Air Cadets, Martial Arts, whatever. If you drive, do your utmost to take them there.
They will talk much more readily if you aren't 'face to face' "questioning them"..... being chauffeur is ideal.