In the new Google Sheets you will find the Add ons menu. This menu allows you to add features to your spreadsheets and documents, much like the script gallery used to allow you to do. The great thing is that the new Doctopus add on is very simple to use and walks you right through the process. The added bonus of sharing documents through Doctopus is that you can set up templates for your students to use, as well as grading them using the Goobric rubric feature.
Check out this video to learn more, or check out Doctupus in the Add ons store: