A screenplay is unlike a novel or stage play. It's primarily visual, which means your students are telling a story through images as much as dialogue.
Showing through action usually works better than telling through dialogue.

The screenplay will hone in on the imagery and emotional aspects of the scene.   See example below.

As you can see, the action is foremost. When the character speaks or makes a sound it's contained within the dialogue.
The action is depicted through images. How can they show the audience instead of tell them?