Bone marrow. The inside of your bones are filled with a soft tissue called marrow. There are two types of bone marrow: red and yellow. Red bone marrow is where all new red blood cells, white blood cells, and platelets are made.
Mine is 8m x 7m (3m is 10 feet, so around 27 x 23 feet). This is normal for an Australian classroom, although there's a fair bit of variation.
Table 1 show that the average size of a school was 86,415 feet and the average total cost was $8,483,937 in year 2000 dollars. The consumer price index urban (CPI-U) was used to update earlier costs into year 2000 dollars. Of the 391 new public schools in the study, Michigan accounted for 38%.