We use a self-consistent mean-field (SCF) theory to determine the behavior of grafted polyacids. In these systems, the charge on a brush segment depends on its local environment and on the pH of the solution. The scaling dependence of the brush height on salt concentration phi(s) is significantly different from that for a brush with constant charge density. In the latter case, the thickness is a continuously decreasing function of phi(s), whereas for a brush of weak polyacids the thickness passes through a maximum. The numerical SCF results show qualitative agreement with predictions obtained from a simple scaling model based upon a block profile with a uniform degree of dissociation.