Something that might be considered as well is when schools became bigger, sometimes their focus changed. With increased industrialization of America, the purpose of many schools became to produce students who were cabable and skilled to become factory workers. The schools were business and educating competent workers was the product.
In the early 20's there was a record number of schools. It was the era of the one room school house. Towards the end of the decade consolidation was the norm and many of the one room school houses were replaced with larger consolidated schools.