Kerry, can I suggest for next year you set a different groups with different enrolment codes for each tutor group. ( I use the groups code for the group and enrolment code).
Make the enrolment code in the settings page a hard one to guess and force groups, that way as they enroll (First time in) they are sorted into groups by the enrollment code. (Saves a lot of time for me) I just check the number of members of a group to see if they have all enrolled, tick off the ones who have from my class lists then verbally bug/help those who have not.
Oh , I also put instructions in the summary page (Settings page)
Example ...
Y7 - KS3 Science homework.
Enrole USING YOUR CLASS CODE (7a1,7b4 Etc. ) IF YOU ARE really STUCK or NOT YEAR 7 enrole using key :- uk
Oh, the uk key puts "Odd, one off" visitors in a separate place so they dont get mixed up in my groups
Hope this helps