A mattress layered Soft on Top and Medium on the bottom is considered a “medium” mattress, will provide plenty of support for small children, and will probably feel a bit more comfortable to him or her than one layered Soft on top and Firm on the bottom. If you have a larger child, or a child who is or will be growing to a large adult size soon (over 180 pounds), you might consider choosing a Medium layer on top and a Firm layer on bottom.