By applying the Advocacy Coalitions Framework (Jenkins-Smith & Sabatier, 1988), this paper shows the results of an applied research that studied how a new selection and hiring scheme for new and in-service teachers of the basic education was introduced in Mexico. As a consequence of corporatist practices, teachers and head teachers' posts were - and still are - offered on the basis of traditional criteria. Then, recent policy changes suggested to replace such model for a merit-based model. As it was expected, resistances from different corners arose and thus, implementation process has been repeatedly blocked. Although some teachers agreed to be evaluated, there are other type of factors that are constraining implementation process such as an inefficient top-down formulation, lack of transparency, weak legal basis and a rudimentary technical support. All these factors have contributed to the formation of coalitions that are clashing constantly, so, policy implementation process is interrupted. This analysis lead us to reflect under what bases different actors with different beliefs and values could cooperate to make the educational system more efficient and, ultimately, modern.