The only way to add a new group of students right now is to add their profiles one by one from inside any of the Osmo apps.
To delete any of the old students' profiles on your myOsmo account, please log into myosmo.com, select 'Profiles' from the dropdown menu under your username, then click any profile icon to go that profile page. Once there, click on the gear icon in top right corner, and select 'Delete'.
If you would like us to assist with deleting old profiles, please send a list of the profiles that you need to delete to us at email@example.com, and we'll do it for you.
Also, if you wish, you can delete your old account (and all associated student profiles) and set up a new account. To delete your account, first go to myOsmo page (https://my.playosmo.com). After you log in, select 'Account' from the dropdown menu under your username (top right corner), then scroll down to the 'Delete Account' section. After it's deleted, you will be able to set up a new account with a new group of student profiles.