Reduce Lag without reducing Graphics Quality?

I am developing a 2D side-scroller for iOS that is working brilliantly in Unity by lags a lot on my iOS device. I know my iOS device has less processing power but I have set the iOS Graphics Quality to Good which is about medium and my graphics are only 192x108 at maximum. I think that the lighting in my scene might be the issue and the use of a Sprite Diffuse material to shade my sprites might be causing the lag. If anybody knows how I can reduce the lag without effecting graphics quality, as I already have, it would be much appreciated if you could let me know how.

Many Thanks,

Tommy Eaves

Two words:

draw calls

Try to combine your sprites using sprite packer.