This is only a problem in "Programme of Study Tracking" which we use to enter grades that then get pulled through into a marksheet to calculate an end of term grade.
No matter which class you filter to, you end up with 10-15 names that teachers don't recognise because they are just applicants to the school and are on SIMS applicant under the status 'waiting list'. So if you choose any Year 7 class to enter their grades you end up with the same 10-15 extra random names; and they'll be different if you select any year 8 class.
I suspect they were accidentally promoted somehow when we did the end of year procedures but i can't find any way to 'demote' them. After a 4 week wait, Capita helpdesk told me to run the database diagnostic tool and closed my ticket.