In Australia we have the year divided into terms. Each term is about 9-11 weeks long with a 2 week holiday in between terms and a 6-8 week break at Christmas. It works welll for the children. If we ever get a 12 week term the little kids are completely exhausted buy that week and you can see they are ready for a holiday. The longer break at Christmas allows families to take some vacation time together. The shorter breaks throughout the year,, give the teachers a rest, time to plan for next term, and gives the mums a break from driving the school run
I don't know how the US manages to keep their kids grades up with the system over there. Over the Christmas break most children in Australia drop back 2 levels in reading and forget a whole bunch of stuff that needs revising. A longer break would mean some after schooling would be essential!
Overall I like the Aussie system, though it does pose some problems finding care for working parents.