Es and Us. Sorry to be blunt, but most schools and most sixth form colleges ask for a minimum of 5s and 6s for A-levels for a reason- because this is the minimum level needed to pass the course.
I would say, really, to have a firm chance of passing (and by passing, I mean an E grade) an A-level in a subject, you need a strong 5/weak6 in that subject or relevant subjects at GCSE. If it's an essay based subject, you probably need a 6 in English as well, and if it's a science based subject, you really need a 6 in maths.
If you want to get Cs or above (usually the minimum needed for uni entry) then you really need a strong 6, or a 7 or above, plus probably an average of 6s across your A-levels.
There are exceptions to this, for lots of reasons- but you don't mention any extenuating circumstances.
To get a 2 at GCSE in any subject is really, really weak- it's not just lack of effort from an able student, it suggests struggling academically in a way that means they are going to struggle with the step up to A-level.
If they are a hard worker, with that grade profile, a level 3 BTEC could be a good route for them, and this could be studied in a sixth form college environment. If they're not hard working and can't stick to deadlines, a BTEC won't work well either though- BTECs are not "easy" and they would need to be prepared to work at it to do well.