At Portage High School, we switched to a block schedule this year. Instead of 8 45 minute periods, we now have 4 90 minute blocks. Classes are either "intensive", meaning they meet every day for half the year, or "A/B", meeting every other day for the full year. All AP classes are A/B.
So far, we love it. All levels of students seem to be doing better, including the low and middle level student. The math, science, and foreign language teachers have all adapted well and most report they are further ahead than last year and that the students have learned the material better. The biggest advantage seems to be a more relaxed school day, so students and teachers are not stressing out.
I teach both AP Calculus (1st year) and AP Physics (4th year) and I love it. The day off in-between gives students time to digest the information and come in for extra help, not to mention they have two days to get the homework done, which is especially nice for students involved in athletic or other after school activities. The 90 minutes lets me answer student questions without feeling rushed and also helps build connections between concepts. I find I waste less time reviewing previous material or giving work time. I teach for pretty much the entire 90 minutes and have found very few students getting bored. Given a choice, I will never go back.
James Marshall physics/math teacher Portage High School