Ofqual blogged (again) about tiers of entry.
They are very clear that if a student is expected to get a 4 or 5 they should be doing foundation. Some subjects no longer have the grade 3 back up on higher any more.
ofqual.blog.gov.uk/2020/01/23/gcse-tier-entry-in-2020/
Check your child's tier of entry carefully!