Dyscalculia is a specific maths difficulty. It is inherent rather than just being ‘weaker’ at maths. A child will display intrinsic difficulties with their quantitative understanding of number at a basic level – i.e. show them 3 counters, then 6, and they could not quantify that one set was larger than the other, nor could they give sensible estimates for each quantity.
As a school, we cannot diagnose dyscalculia. This would fall to an Educational Psychologist or a certified assessor and would likely be a private educational diagnosis.