A sizeable literature has argued that the growth effects of changes in flat rate taxes are small. In this paper, we investigate the relatively unexplored area of the growth effect of changes in the tax structure, in particular, in the progressivity of taxes. Considering such a tax reform seems empirically more relevant than considering changes in flat tax rates. We construct a general equilibrium model of endogenous growth in which there is heterogeneity in income and in the tax rates. We limit heterogeneity to two types, skilled and unskilled, and posit that the probability of staying or becoming skilled in the subsequent period depends positively on expenses on “teacher” time. In the production sector, we consider two sources of growth. In the first, growth arises as a purely external effect on account of production activities of skilled workers. In the second, a portion of the skilled workforce is used to work in research and other productivity enhancing activities and is compensated for it. Our analysis shows that changes in the progressivity of tax rates can have positive growth effects even in situations where changes in flat rate taxes have no effect. Experiments on a calibrated model indicate that the quantitative effects of moving to a flat rate system are economically significant. The assumption made about the engine of growth has an important effect on the impact of a change in progressivity. Quantitatively, welfare is unambiguously higher in a flat rate system when comparisons are made across balanced growth equlibria; however, when the costs of transition to the higher growth equilibrium is taken into account only the currently rich slightly prefer the flat rate system.