After student writing has been peer-reviewed or graded by teachers, you can export the writing to to one Google Doc, which allows you to print it.
1. Go to 'Report' and click 'Export'.
2. Choose 'Export writing & grades to Google Docs'.
3. The writing will be created as a new Google Doc in your Google Drive. You can open it, then click 'File' then 'Print' from inside the Google Doc.