I find the school system quite confusing since I haven’t been there for many many years now. My newphew is 4 and started school in September, his handwriting from what I’ve seen is about similar to Ru’s, maybe a bit better but that could be because he’s been in nursery for years due to the fact both parents work full time jobs so the nursery could’ve started working on that with him earlier. I have a niece on my partners side who is the same age too, and hers is pretty good too but she was in the same situation, nursery from a young age due to parents working full time. I think child intelligence just varies from circumstance and how sociable they are.
If Ru is intellectually stunted for whatever reason, it’s most likely Gemma’s fault, kids learn from their surroundings and being around adults. Up until a year ago he only had Gemma, who also isn’t the brightest spark.