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:
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.
Using your favorite browser - we always use Chrome: