hi Sheila - I often use SQA Numeracy level 3 questions as a guide to which areas learners feel confident with... delivered in a low key, informal way, it can lead to a list of targets for an ILP eg I want to feel more confident with %, fractions, when to divide, decimals etc
For writing, I encourage learners to come back next week with half a page about something they really know/care about (their dog! their holiday....) and not look up any words, but think as they write about using capitals and full stops. Any words they're not sure about, its fine to do a wiggle underneath to show that they thought it didn't look right etc
Then, when they bring this piece in, I'd do error analysis and see how much they understood about spelling rules, use of capitals and full stops etc - again this would lead to ILP targets.
Less sure how best to assess reading ...