You only have to walk through the school to appreciate that they are far from sad, impoverished places.  They are busy, hard-working and joyful places.  Furthermore, there is a discipline in the classroom that would be the envy of many teachers I know in the UK !  
Timekeeping turned out to be one of the worst bugbears for us.  We come from a culture in schools where every minute of school time is accountable and if you leave a class unattended you risk severe disciplinary measures.