The child stands apart. The difference lies in what it feels while doing so. A shy child wants to join in but does not dare — and once someone takes it by the hand, it joins after a while and is happy. A child who does not understand the unwritten rules cannot join: it does not know how to start, misses the other children's signals, and playing together drains it rather than pleases it.
Unwritten rules cannot be learned from an explanation — an ordinary child picks them up by watching. When that ability is weak, the child sees the same playground as everyone else but does not know what is allowed in it. That is why advice such as “go and ask them” does not help; the problem is not courage but a missing manual that the others never needed.
The detailed screening covers five areas — communication, reading other people, rigidity, interests and sensory overload. It is their combination that separates a shy child from one who does not understand social rules, and it shows where to start.