Parakeet Nesting Box?

I bought a nest box for my parakeets and i dont know if its any good. It looks like the one in the link. http://www.smarter.com/bird_bedding_prod...
The problem is my birds always go on top of it and try to carve it out. They never try to go inside of it. I was wondering if the box should have a perch on the outside or inside because my parakeets box has a perch in the inside and why they keep on trying to carve it out.
Answers:
I did not look at the box you have posted. From experience, though, a perch outside is a good thing. The female or the male will sit outside and feed the other adult inside from the perch and also sing to it inside the box. The bottom of the box should have a small cavity carved out of it and things for the babies to grab onto with their feet when they hatch (wire grating works, just make sure there are no sharp edges), otherwise they will get 'splay-legged' and will not be able to walk or sit on a perch.