In terms of staffing, Jen, it is important to remeber that often, primary schools will have one TA across the school. Also, many TAs these days also double up as lunchtime supervisors to bump up their appalling wages so aren't available at lunchtime anyway.
Oh, and we are often in at 7.30 in the primary sector too you know. In fact, as I have taught in both and have no axe to grind I can honestly say I saw far more 'arriving as the kids do' in secondary than I ever saw in primary. In primary, I think the latest anyone arrived was about 8.15 with the vast majority in before 8am for a 9am start.
I also remember how often I tried to contact someone at the local secondary with regards transition and couldn't get hold of them even though it wasn't even 5pm yet!
I'm not playing oneupmanship. As I said, I've worked in both sectors. Far, far more marking in secondary (I taught English) but it was nice to have a change over every hour. Oh and to have free periods! Though the advent of PPA in primary has helped counter that somewhat.
The biggest difference I found was that the kids I was teaching at KS3 were streamed which makes the lesson more effective. It is hard going with a class of 34 Y6s when you are trying to teach some how to use the passive voice and how this can manipulate a sentence whilst you also have one or two others who still don't know what a verb is.
Differentiation and making sure all children are actively included in each lesson is definitely far harder at primary level.
But hey, I'm now happy as can be as a TA. I still get to teach lots, which I love, but I no longer need to have anything to do with the politics or the paperwork. I'm fortunate not to need the money so it's win win for me!