An image forming system which is capable of causing a clear coating apparatus to discharge processed sheets in proper page order, and improving usability and operability of the system by users. An image forming apparatus is set to perform single-sided image formation or double-sided image formation. A clear coating apparatus is set to perform single-sided clearing coating or double-sided clear coating. Whether to perform inverted discharge of sheets is controlled according to the settings of the image forming apparatus and the clear coating apparatus.