OP, the problem is nobody knows what maths assessment your DC took at school. There are numerous maths assessment packages available to schools; GL, Rising Stars (PUMA) and Pearson to name just a few. A score of 90/110 could be average, good or outstanding, but it is meaningless without putting into context - both in terms of the assessment and the attainment over the year as a whole.
As it is coming to the end of the school year, I am assuming you have a parents' evening approaching; my advice would be to ask your DC's teacher how they are doing, not Mumsnet.