Common Core Standards
Grade 4
Writing W.4.3.B
Use dialogue and description to develop experiences and events or show the responses of characters to situations.
Reading dialogue helps students write dialogue. Even better if you can get students listening to the ways that speech works and sounds in real life. But it's often difficult to transfer that directly to the page.
What your kids can do right now—without loads of practice—is predict human behavior. They'll be able to decide how characters will respond to events and situations. Don't get too picky about the stilted dialogue of many young writers, because any work put in will prep them for further literary work.