Other factors, such as amount of review and qualifications of the teacher, did not appear to be related to differences in achievement. Rice is method, which relied on inspection of the characteristics of high- and Low scoring schools, did not allow him to estimate the strength or shape of the relationship between some hypothesized factor and the level of achievement; it permitted him only to say that because not all the high-scoring schools had a characteristic that the low-scoring schools lacked, s or vice versa, there must not be much of a relationship. Surprisingly he found what he termed a controlling factor: the system of examination used to assess the teacher's performance.t