Earlier quoted context omitted.
I completely agree that age-based classes is stupid. But what's the alternative? The idea of classifying 5 year old kids based on any kind of factor scares the hell out of me.
Erm, what scares you about ability-based classes? The single strongest motivator for me to do well at school was to get into the top set which was free from bullies.
This system works out very well for bright, academically inclined students, sure. But it sets a structure of expectations that don't motivate what could possibly be great talent, but we wouldn't know because they didn't bubble in the right answer.