Oh my goodness! This thread makes very interesting reading, because it demonstrates how the general public has been hoodwinked by SATs levels. Firstly, before SATs were abolished, it was impossible for a child to be a Level 8 in English or Science, as the tests only went up to Level 7. If a school judged a child to be Level 8, it was because they were using their own system and was absolutely nothing to do with national criteria.
Secondly, levels in KS3 have never been officially subdivided into three categories. If a school claims a child is Level 5a rather than 5c, the teachers have made up their own descriptors. There is absolutely nothing scientific or official about it. What a 5a generally means is that the teacher's gut feeling is that a pupil is easily within the band for Level 5 and possibly achieving at Level 6 on occasions. To be honest, the way level descriptors are written, there's no concensus about what they mean anyway.
Thirdly, termly progress levels are often, at best, a "guesstimate". Individual pupils just don't progress through levels at an even rate and teachers rarely have the time to assess every single pupil against every single descriptor. What seems to happen is that targets are based on performance at KS2 (and some other factors). The reality is that teachers look at the targets and performance in the last progress check. To avoid worrying parents, a wise teacher makes sure that there is an indication of progress (ie. the level is at least as high as the last one) and fits in with the eventual target. Again this is based on gut feeling and experience. Levels were never intended to report progress to parents, except at the end of key stages.
An additional problem with targets based on KS2 levels, using what is known as FFT data, is that if a child is already underachieving at KS2, the target will be lower than the level a child could potentially achieve and could hide underperformance. There are also pupils who work conscientiously at KS2 and cope well with the demands of the basics, but do not have the ability for more abstract and conceptual thinking. It simply is not true to assume that every pupil will make even progress at approximately 2/3 of a level every year throughout his/her school life.
There's an awful lot more to education than levels!