We investigate the von Neumann entanglement entropy as function of the size of a subsystem for permutation invariant ground states in models with finite number of states per site, e.g., in quantum spin models. We demonstrate that the entanglement entropy of
n sites in a system of length
L generically grows as $\ensuremath{\sigma}\phantom{\rule{0.2em}{0ex}}{\mathrm{log}}_{2}[2\ensuremath{\pi}en(L\ensuremath{-}n)∕L]+C$, where $\ensuremath{\sigma}$ is the on-site spin and
C is a function depending only on magnetization.