The local high school does all classes on Monday for like 20 minutes each (it's also the district wide early release day) and then four days of 90 minute class periods.
My kids went to a private school that had three days of 45 minute periods and two days of 90 minute periods. They hated the block days because the classes seemed to drag on and on. I hated the block days because the teachers seemed to do 45 minute lessons and then nothing for the rest of the period. The only teacher who was able to use the block period effectively was the science teacher.
