We study the ground state and the phase transitions of the bilayered s
pin-S antiferromagnetic Heisenberg model using the Schwinger boson mea
n-field theory. The interplane coupling initially stabilizes but event
ually destroys the long-range antiferromagnetic order. The transition
to the disordered state is continuous for small S, and first order for
large S. The latter is consistent with an argument based on spin-wave
theory.