Hi wii man,
I built a nest box at scool too,(long time ago now) the teacher made me paint it and when I took it home and hung it in the garden the birds was just not interested.
My big brother said maybe they dont like the colour sceme (sky blue with a white roof), anyway so we sanded it down and sure enough, we saw some sparrows checking out the des res in the following febrary and by april/may we watched them building a nest, later we saw them fly in with beak-fulls of grubs and we realised they was feeding chicks.
I think you really need to be patient and dont expect to see much too soon!, let it 'weather in' a bit and face the hole eats or north, so that the midday sun dont make it too hot for them. Good Luck Tbird+