Unfortunately, there is no way of knowing the percentage weightings for the subjects tested in the Trafford CEM Test – it is not in the public domain.
However, I do know that each of the schools (AGSG, Sale, Stretford & Urmston) standardise differently from each other and they also weight parts of the CEM Test differently. This means it is perfectly possible to pass one school’s exams and fail another. Last year in order of difficulty AGSG came out as slightly harder to pass than Sale, by approximately 5 marks; then Urmston and Stretford were both easier to pass than Sale Grammar – by approximately 10 marks. This was for EXACTLY the same test taken (data taken from my 24 student who took it).
Nets of cubes could be tested as part of the CEM Test. Try using CGP and Letts 11+ workbooks to practise these.