In the past, depending on which measure was used, researchers tended toward far different interpretations of the benefits of class size reduction leading to far different recommendations for implementation. In 2002, Margaret Spellings, secretary of education under President George W. Bush, pointed out the need for a standardized definition of what is meant by class size.
To differentiate student-teacher ratio and class size, it is important to know several key distinctions. Class size, generally speaking, refers to the average class size in a given grade level of a given school. Student-teacher ratios, normally, are calculated by taking the total number of teachers at a given school divided by the complete enrollment of that school. This distinction is significant, because the ratio will not always match up with the class size figure (or vice versa). For example, a student-teacher ratio may be small but a class size may be larger than what the student-teacher ratio leads one to believe.