I have found stuff on block learning, but nothing about taking 3 weeks of 2 subjects, then starting with another 2 subjects for 3 weeks, then going back to the original 2 subjects.

So math and english for 3 weeks, then chem and geography for 3 weeks, then math and english for 3 weeks, then chem and geograhy for 3 weeks, then there are 3 more weeks until the trimester ends.