First its important to understand that year long school could mean several different types of schedules. It could be 3 weeks on and 1 week off throughout the year with a few longer duration breaks during the holidays, spring, and summer. Also you said something that needed to be defined. Broken is something that is not working. Students in the US have shown to be behind many nations so it is reasonable to say that it is broken or at least breaking down compared to other nations. There are successful students in every school, but more could be successful schedules were adjusted to allow less time to forget lessons. In addition, it doesn't work too well to review last year's content for up to a few weeks in the current one.