As a K-8 technology teacher, my students in grades 2 and above use Scratch. Rather than each student having their own Scratch account, I have a single account for our Computer Lab. I may break this up into an account per grade in the future but there still will not be accounts for each student.

The way that Scratch currently works, multiple students could be logged in to the single account all working at the same time. I chose not to do this, however, because then students have access not only to their content but to the content of others and to the Studios, etc. that I use to organize student work.

Instead I have my students work on their Scratch projects without being logged in (using the online version not the installed offline version) and then when a project is completed, it is uploaded to our Computer Lab Scratch account. To do this I will:

Log in for the student and then have them save their project and sign out as soon as their project is saved OR
Temporarily change the password and have the student log in and save their project and sign out as soon as their project is saved OR
Have students let me know that their projects are complete and I will upload them over our network myself.

I have not found that one of these is better than the other in my case. It's more a function of timing. If a class is almost over it's easier to go with the 3rd option. If students seem to be finishing at intermittent times during a class, then the first option works well. If an entire class (or most of the class) is finished, then the 2nd option is the best fit.

One disadvantage to working on Scratch projects this way is that students don't have access to their Scratch projects at home should they want to work on them there. To get around that and allow students to work on their projects at home, what they need to do is send themselves their Scratch file (the extension will be .sb2) somehow or save this file to a flash drive. My students use the Edmodo backpack for this. Students can upload their Scratch project file to their backpack on Edmodo at school and then download it at home. They can then go to the Scratch website and work on their project. When they are done, they would follow the steps for saving their Scratch project to their computer and then upload it again to their Edmodo backpack so they could download it at school to work on it. Yes, this is multiple steps but it does work and gives students good practice in uploading and downloading files.

This Instructable will show how my students work on their Scratch projects using the online editor without logging on to Scratch.

Step 1: Creating a Scratch Project

Using your favorite browser - we always use Chrome:

Go to the Scratch website at http://scratch.mit.edu/
Make sure that you are not signed in. You should see Sign In in the upper right-hand corner.
Click on the Create option.

Step 2: Open an Existing Scratch Project

If a student is just starting a new project, they would give it a name where it says Untitled and begin editing but if they have previously started a project and saved it to their computer or the school network, here's how to load the existing project:

Click on the File option.
Click on the Upload from your computer option.

This will allow the student to browser to a folder on their computer or on the network to find their saved project and select it to be opened. Once they select their project to be opened, they will see the Replace the contents window and they should select OK here to open their project.

Step 3: Save a Scratch Project

If students are logged in to the Scratch website, their project is saved periodically as they edit it. If students are not logged in (as is the case with my students), they need to make sure to save their work then they are done or at the end of a class so they can continue working on it. There is no Save option nor is there the infamous Floppy Disk icon. So, how do students save their Scratch projects:

Students should make sure that they have named their project. They do this by typing the name where it original said Untitled above the Scratch stage. I have a naming convention in my lab in addition to folders where things are saved. Our naming convention is Grade-StudentName-Assignment Name (which I give them).
Click on the File option.
Click on Download to your computer to save the Scratch project. This will allow the student to navigate to the appropriate location and save their Scratch project.

Since students are not logged in to the Scratch website, they will receive a warning message if they try to navigate away from the Scratch website or if they try to close out of their browser. As long as they have completed the steps above, it is fine for them to choose the Leave this Page option.

Step 4: Share a Completed Scratch Project

Once students have finished their Scratch project, I do want to share them online and here's how I handle that with my classes:

Log in for the student and then have them save their project and sign out as soon as their project is saved and shared OR
Temporarily change the password and have the student log in and save their project and sign out as soon as their project is saved and shared OR
Have students let me know that their projects are complete and I will upload them over our network myself and share them online.

I have not found that one of these is better than the others in my case. It's more a function of timing. If a class is almost over it's easier to go with the 3rd option. If students seem to be finishing at intermittent times during a class, then the first option works well. If an entire class (or most of the class) is finished, then the 2nd option is the best fit.

The 1st image shows the sign in screen that students (or you) will see when you click the Sign in to Save or Sign in options on the upper right. Students know our class user name and I will either type the password or will change it temporarily and tell the class or write it on the board so they can find it to log in themselves.

In the 2nd image you can see that once you log in, there are additional options of Save Now and Share available. I have students Save and then Share. I then have students click the See Project Page button.

The 3rd image shows the Project page. In some cases, my students need to add additional directions about how their project works or they need to add credits for images used on this page. I always have my students (if they do the uploading) turn off commenting on their projects. I have not seen a lot of spam or inappropriate commenting on the Scratch website but still turn this off on student projects.

Step 5: Add Projects to Studios

As you can image having a single account for the Computer Lab can mean that there are a lot of projects to manage. I work in a very small school so it's not too many but I still use Studios within the Scratch account to organize the uploaded projects.

Once you are logged in on the Scratch website, you can click on the My Studios option to see any existing studios you have created or to create a new studio by clicking on the + New Studio button. I have studios for each class and studios for various projects that multiple classes have completed. A project can be in multiple studios at the same time. I don't, typically, have my elementary students add their projects to Studios but often will have my Middle School students do this on the Project Page when they are adding credits or instructions.