The sign also illustrates a woeful trend in signalisation. (See f.e. also Denmark, Slovenia.) These are countries who adhere to the modern view about communication. Because people can't stand a message loud and clear, today's communication must be fluffy.
A nice wrapper is needed, some mollification, a smile. A bit like our food. Try to find a honest potato. Everything has been processed, improved, made fat free. While this approach surely makes it easier to swallow the dailly killings on our television screens, it is a bad idea for traffic signalisation.

Roadsigns must transmit an unequivocal message in a split-second. The older signs perform much better in this respect.

The pupils are mostly shown walking.
The boy prefers long trousers but is sometimes seen with shorts. It then becomes clear that he failed to get one of his socks —The bulge halfway on his leg could also be the fur collar of a boot, but his mom would have stopped him then, I hope. (hiss from M. Jean: Role confirming)

When walking, the boys carries a book bag. I'm not sure about the girl. In jogging mode the girl is without and the boy likely so.

Several European countries grow similar stock (e.g. Spain).

The girl is dancing her way to school. She wears the same hairstyle as her compeer in Denmark. She didn't grew up like the boy. He grew taller into a more adult stature while the girl became more childish.

The boy switched his bookbag for a ruck-sack. We have seen this boy earlier! (Find him in Giumri - Armenia.)

It's apparent that Bulgaria has quite some difficulties in keeping to quality standards. Sloppy work abounds and the poor kids are rapidly becoming weird creatures with spikes and impossible body parts. But still, I prefer this poor drawing above the flat iconized versions of most countries.

Other countries with girls much smaller than boys: e.g. Czech Republic, Nepal.

The speed allowance is rather high. Many countries prefer the limit around 30 km or below (see Australia for a short overview).