I found it useful to go through the school's website with them, discuss the rules, club options, look at different subjects. I found it helped them feel prepared.
We also practiced and timed the different routes they could take to and from school.
I gave my kids a bit extra for breaks/lunches during the first few weeks so they could try out new things, then we'd discuss what they liked, didn't like, anything from home they might want to take in instead.
I'd also recommend some grab and go breakfast and snack options for them to have at hand. All of mine went through times of not wanting breakfast at home and just grabbing something on the way out.
As others said, it's normal for them to be quite tired and also emotional. I found my sons particularly struggled emotionally with the shift at first - my younger son struggled a lot through most of Y7 emotionally with the changes and the behaviour of his classmates, with my daughters hitting it more around Year 8 as their first secondary friendships were starting to have issues they'd never had before.
Is secondary kids getting Costa a thing? That is something I hadn't anticipated but has been mentioned twice now 😂
Not Costa, but 2 of my kids went to a school that had a LIDL built nearby and it became normal for some kids to grab bakery items from there on the way in.
My oldest and youngest went to schools near the train station, and with my youngest, his key worker ended up talking to me about him regularly picking up things from the train station shop on his way in and how it was normal due to their location to see which first year kids having that freedom who were then coming down from sugar crashes or caffeine. We ended up putting in a new, bigger breakfast that he makes for himself the night before to grab and go to help him.