light projecting through walls

I have come across a situation concerning lights that I can't seem to rectify.
I have a large room separated into two by a roof to ceiling wall, 4cm thick.
On the far side of the wall, I have a number of area lights in cylindrical form to simulate flouros.
There are also objects such as balconies and railings.

when looking at a quick render from the outside, the balconies and railings can be plainly seen as if projected onto the wall.

I have played with settings of the lights and the wall, but cannot fix it.

The texture on the wall is a UVW map of wallpaper.

Thank you Brian, played with the lighting settings, disabling the ambient illumination helped.
It also helped with the other problem you mentioned, light spill with thin single poly walls.