The Add Multiple Users plugin is a useful tool to create sets of logins in bulk (See this article). It is also useful to move users between blogs or add users to multiple blogs.
This is best done in a meeting with all teachers who will need to bring a class list with them. In this way the whole operation can be completed in less than half an hour. Otherwise an individual will need to shift users into each new blog one blog at a time. Show teachers the process and ask them to make a list of missing or new children as they go through. Any missing or new children should be added by a Network Administratorfrom the Network Admin menu Sites > All Sites > Edit > Users Tab > Add New User
To add a set of existing users to a new blog, first go to the dashboard of the new blog. From the sidebar menu click AMU > Add from network
Here's a video to show you how:
Note: you can use this method to add teachers, TAs and children to a new blog in one go. Simply ignore the “set role” box above and set the roles of each user as you add them.
Always check that the users accounts have been successfully added to the blog by clicking on Users and checking the accounts are in the list for the blog. The most common mistake is to forget to set the role using the “Set Role” box at the top, in which case the children will all be set as Administrators in their new blog. If this is the case, select all the users with the incorrect role and use the “Change role to” drop down at the top of the users page to set them as contributors.