Before migrating students, it's recommended that you have all the information in front of you showing which students will be moving to which classes, and which teachers they will have.
To get started you will need to create your new class, you can find out how to do this here.
After creating your new class, select Classes from the left hand menu. You can search for the class from the filters. Select the class you wish to migrate. Across to the right you can select ‘Migrate Class’.
From the dropdown select the class you wish to migrate students to. Select the students you would like to migrate.
If particular students are not to be migrated to the selected class, you can deselect them by clicking the ‘x’ next to their name.
Click Migrate Students.