What is meant by lower class boy and middle class measuring rod?
This was a phrase that was coined by Albert K. Cohen in his 1955 publication Delinquent Boys. In that work, Cohen examined subculture theories as they related to criminality and delinquency. He studied young men who lived in economically disadvantaged neighborhoods but who were judged by standards used to judge more affluent groups of young men in higher socioeconomic classes. Critics of this study argued that you were not comparing apples to apples, so to speak.
In other words, when people come from different socioeconomic backgrounds, it is impossible to determine similar causes of delinquency because the individuals have access to very different levels of economic support. Lack of money for some individuals is a determining factor for delinquency and further criminality.
Crime and Criminology/Reid/p. 129