I'm with the OP too, despite having tried all the types of questions proposed, and I've read 'How to talk so kids will listen and how to listen so kids will talk' - I get vague answers at best (and DS is in Y2). Vague as in:
Me: Did you do any maths today?
DS: Yes. No, not really.
Me: What do you mean?
DS: Well some of us did. I think.
Me: How about you?
DS: I don't remember.
...
Luckily our school sends weekly newsletter with a 'children's week ahead' section that covers, in a few sentences, what each year group will be covering in Maths, English, Topic, and sometimes Science. So on a good day the conversation might continue like this:
Me: Well, the newsletter said you'd be working on telling the time this week.
DS: We didn't do that!
Me: Are you sure?
DS: Yes! No, actually, red group were working with Mrs X, I didn't see what they were doing, perhaps they did that?
Me: Ok, so what were you doing while red group was working with Mrs X?
DS: Blue group was 'working independently'.
Me: What was your work then?
DS: What do you mean?
Me: Did you have a work sheet, a problem to solve, something to read, ...?
DS: I think we had a work sheet.
Me: So what was it on?
DS: I forgot.
Me: Perhaps it was on telling the time?
DS: .... [memory finally triggered] oh, yes, it was!
That's the best I get. Ongoing questions as to what exactly, how easy/hard, anything interesting, anything learnt ... draw blanks. 95% of the time.
So with lots of quizzing, which annoys him and we both find tedious, I can 'find out' pretty much what I know already.
I think many teachers (and parents whose children are more forthcoming with information) underestimate just how much many parents are in the dark regarding what goes on in school.
For example:
Teacher to parents: Each child is given their own learning goals. They are stuck in the front of their books. We discuss them with the children, go over them pretty much every day. Your children know their learning goals. Please do ask them about them, and ask them how they are getting on.
Head teacher to parents: We are very keen to work in partnership with the parents. Please do discuss your children's learning goals with them. It is great if you can support them in achieving their goals. We welcome your feedback, please let us know if you feel your children's goals are too easy or too hard for them. But don't worry, we make sure that every child is appropriately challenged, and even if it seems very hard for a child initially, you'd be surprised at what they can achieve!
Me (to DS): So what are your learning goals in maths?
DS: Learning goals?
Me: Yes, Mrs X said you had learning goals, she said you'd know them.
DS: What are you talking about?
Me: They're stuck in the front of your books. You go over them often.
DS: There's nothing stuck in front of my books.
Me: Why don't you have a look tomorrow?
Next day
Me: Did you check if you had learning goals stuck in the front of your books?
DS: No, I forgot.
Repeat last paragraph several times.
Finally:
DS: Mum, I checked, there are indeed learning goals stuck in front of my books!
Me: Well done for remembering. Did you read them?
DS: Yes.
Me: Do you remember what they say, for example for maths?
DS: No. Yes. Hang on... I think it was just the normal stuff.
Me: What do you mean, normal stuff?
DS: Well, the next steps and stuff.
Me: So what are your next steps (and stuff)?
DS: I forgot.
Along comes parents evening, we have the opportunity to see the books. There are indeed learning goals stuck in the front. With a date for when they were set, and a date by which they should be achieved. Unfortunately the goals are things that DS could do backwards in his sleep when they were set. But now, a term after they were set, it is a bit late to do anything about that.
If schools mean their 'partnership with parents' talk, then they need to acknowledge that a good number of parents rely on info from the school in order to be able 'work in partnership' in any meaningful way at all.
Should homework be the means to pass on such info?
Well on the one hand, in addition to learning what specific topic they are working on, homework lets me get a feel for how difficult/easy my child is finding it. On the other hand, as I don't have any points of comparison, I don't know how hard they should be finding it. E.g. is it differentiated homework, so all children should be finding it a little bit challenging? If DS whizzes through it with no problems at all, is that because... a) he's able in that topic and everyone got the same, b) he should be in a different homework 'ability group', c) the homework was meant to be easy, to build confidence, ...? So no, in actual fact it doesn't tell me very much at all.