a) Pretend that they are not there and just leave them as a totally unusual space where mischief can often happen. These areas are usually out of sight and a magnet for potential misbehaviour. In the worst case there are low barriers of what look like scaffolding poles to keep people out. All this does is create a very silly, ugly and wasted area. In the photograph below from a school with a very sculptural wooden stair case in the middle of a large commons area, there is real wasted space underneath, guarded by a low rail.
c) Thirdly, and most usefully, put the stairs where they can be seen and passively supervised - and then use the space for learning - creating a small area for quiet social space, learning intervention or small group work. With carefully designed stairs, and considering all the H&S issues, these spaces have the potential to enhance the school environment.
It's a pity that more schools do not think about the potential benefits of these areas from the very beginning.