Never.
I have asked repeatedly to see them at parents evening but I may get a glance from across the table in one book if I'm lucky and write to request beforehand.
School recently plummeted from Outstanding to Satisfactory and the progress with one of my dc was appalling(wasn't told about that either,only found out on asking for levels),writing level in another isn't v good either imvho,another lacks confidence in maths so seeing her work could help but sadly no.
On speaking to the head re seeing the books and a few other things like lack of rather important info,consistency,low expectations etc he said "take your dc elsewhere if you don't like it,we know we're outstanding so you shouldn't feel the need to want to see work or ask questions".
Soooo I guess that's kind of it then re seeing work.
Personally I think it should be mandatory.When I was a teacher I used to love sharing work,showing off how far they'd come,using it to explain things etc.I used to put all their books in their tray and stack them in order of appointment so no peeking from other parents. Put them in a pile outside the door so they could peruse as long as they wanted. Parents then brought their child's tray in for us to discuss. Seemed to be the norm in most schools,maybe things have changed.
Isn't that difficult imvho.