There is a relatively small pupil to teacher ratio which becomes smaller at the secondary level. Yet this coexists with large average class sizes. The only reason for this dicrepancy I can think of is that there is a huge number of high-schools with 1-20 children in total, in islands and mountainous areas. These have a small standing population but have to have a complete set of high-school teachers nonetheless. Also there is a huge number of part-timers of teachers paid by the hour, a trick to fill in the big gaps that existed in the school system. In real cities class size was ~20-25 pupils per class and is nearing 25-30 as parents are abandoning private schools en masse.

I think the relevant measure is public expenditure on education as a % of GDP. This does not show that Greece is spending too much on its teachers. The meme that Greece has too many teachers was started by a neoliberal politician named Stephanos Manos, who I really doubt knows a single person who sends their children to public school, so he has no first-hand experience. He saw some numbers somehow and was shocked that the plebes might be spending too much... My children go to a quiet suburban elementary school, where class size shot up from 19 to 23 this year. First grader numbers were up at ~25+ IIRC...

As for the quality of the school system. At primary level it isn't too bad, from there on it deteriorates, not least because Lyceum (the three years before one can take exams to enter the University) has been degraded to prep-school for higher education, and because the methods an strategies used are idiotic. Also because preparatory private schools have usually a much smaller pupil to teacher ratio and because it is a national neurosis. That would have been a separate diary but right now I don't expect that there will be much of a school system left after the cuts. Many schools already can't afford heating. Most schools haven't received the textbooks they are supposed to be teaching. At our children's elementary school the parents chipped in to buy soap and toilet paper. And things are getting worse.

BTW Sweden's public sector is now much, much larger than Greece's ever was as a percentage of total workforce...

The road of excess leads to the palace of wisdom - William Blake