This paper seeks to understand what drove the trends in learning outcomes in Argentina between 2000 and 2012, using data from four rounds of the Program for International Student Assessment. A year-specific education production function is estimated and its results used to decompose the changes in learning outcomes into changes in inputs, parameters, and residuals via microsimulations. Estimates of the production function show the importance of socioeconomic status, gender, school autonomy, and teacher qualifications to determine learning outcomes. Despite an important increase in the level of resources invested in public education, learning outcomes in public schools decreased vis-a-vis private schools. According to the results presented here, the increase in the number of teachers in the system, pushing the pupil-teacher ratio in Argentina to 11, had no effect on learning outcomes. The microsimulation further confirms that changes in the system's ability to transform inputs into outcomes accounted for most of the changes in test scores. Overall, the study shows the ineffectiveness of input-based education policies to improve learning outcomes in Argentina.