It's not really a big deal. There will be 3-5 sets, given labels such as colours, animals or shapes, NEVER numbers, letters or top/middle/bottom. The staff may differentiate them as supported/core/extended, or similar. Core will always be the biggest, and may be further differentiated into 2-3 sets.
They may sit mixed, or at their group tables; they will all have the same input, but may get the same work, or differentiated work.
They may be with the same group if children for both maths and literacy subjects, or they may be with different children. The sets are not fixed (fixed setting is called streaming - that does label a child IMO).
The children do eventually work out which set is the most able children, but usually are happy not to be given/think it's not fair that they are given the 'harder' work!
IME of 3 schools, I've never heard anything like "I'm not clever enough for blue table" or "the hexagons are thick".