There is no point at all in sports day. It achieves nothing at all for anyone.
I'm sorry, but I think that is a worrying statement coming from a school governor (which I think you said you are, Luckygirl)
Of course it has a purpose and, if run on more modern lines, as some schools do now, there is something for every child if the circuit games are included. It encourages teamwork and there is absolutely nothing wrong in healthy competition either.
No child should be humiliated and all should be encouraged to 'have a go' at something. Teachers who allow humiliation of children should be brought to task.
Having sat through some excruciating musical afternoons at primary school where every child is encouraged to participate in some way and loudly applauded too I might ask what is the point of them.
If sports day is pointless then we might as well forget all competition, Olympics, other Games etc.