I have a DS in Pr 1 this year. Although he is already very chatty by nature, I find that by asking lots of Qs about his day in school which entails him sharing details etc, it allows all of us at home to know alot about what’s happening in his class and in school.
Preferably when asking Qs, ask leading Qs – ie. not Qs that just entails a "fine" "ok" or yes /no" responses. So for instance Qs like; "what are the names of your classmates who sit beside you in class?" "what did you do during PE lessons", "what was done in art & craft class today?" "what was for recess today – what did you buy?"
From the answers that he gives ask more leading Qs again – and from there you will gradually get to know the names of his friends, how classes are conducted in class, whether anything in particular happened in class etc. Thereafter, you could continue asking more leading Qs, cos you would already know some of his friends’ names, what they do in classes – so more Qs can be framed aorund those details.
I find that once DS gets used to sharing details in school, cos he knows we are all interested in what he does in school, he is very keen to share everything that happens each day. Likewise, everyone else shares how their day was etc, and eventually it becomes a two-way process. It’s a gradual process but eventually the child will learn to "communicate" and share what happens during his / her day.