In every school I have worked in, there have been parents who ask what a report with NC levels actually means. Even with the shifting of terminology (with current levels being abolished and the numbers 1-9 arriving in their stead), understanding the principles behind reporting is useful for any parent or student (or even teacher!).
Firstly, students are granted a target based on previous academic performance. This can be KS2 data, as it is deemed to have external validity (although this is not always the case). Students who achieve a level 5 at Key Stage 2 do not translate that easily to Level 5 at the beginning of Key Stage 3.
In lieu of KS2 data comparison, these targets can be set on CATs data. Such targets are definitely stretch targets, as the CATs are conservative.
While students are given definitive targets, the best targets to give might be ones based on the percentage chance of students with similar academic performance (according to the data) achieving a certain grade. This is ideal because students who are target a C based on previous performance might achieve an A if they are that 2% of students with those previous grades who go onto achieve an A.
The most important aspect of teaching is progress. Teachers are not responsible for student progress (you can lead a horse to water…). However, they are accountable, and are (in my eyes) expected to go beyond expectations for students who need intervention. Such prioritisation needs to be professionally judged, as (of course) this leads to other things being deprioritised.
The general level of progress expected is two sub-levels per year on average. Of course, in English this is hard to discern. In addition, such sublevelling was not initially advised in the creation of levels. However, it allows some accountability of progress. Particularly if stringent moderation takes place.
Targets between subjets?
Levels are not equivalents. Essentially speaking, at the end of Key Stage 3 (Year 9):
A level 5 = C
Level 6 = B/A
Level 7 = A/A*
Level 8 = Not generally given in English.
However, in Maths, a Level 7 leads onto a C. In MFL, students cannot achieve higher than a level 4 (because although level 5 criteria of different tenses can be taught, students do not necessarily have an understanding of those tenses).
So, to summarise:
a) Focus on the progress made from the start of the year: not necessarily on the beginning or final targets (although be aware and see point d).
b) Ask your child if they understand the criteria needed to improve a specific level. Help them with this – all specifications and (nearly all) markschemes are available on the internet, or from your teacher.
c) Targets are not equivalents. Look for progress in your child.
d) Understand how your child’s target has been set: is it based on past achievement? Was that teacher-set or externally verified? Does that matter?
e) What is your child doing that links with the work of students who complete A-grade pieces?
f) Targets are not ceilings: if possible with FFD data (only available in the UK system, although there might be equivalents) see what percentage of students achieve what grades or levels having achieved that previous academic performance: your child might be one of the higher percentile performers. Hard work from them, coupled with useful criteria and feedback, engenders that chance.