<p>Generally the policy on accepting undergrads into the same school for a PhD is determined on a departmental basis. I know my undergrad department was fine with it (one professor told me if I ever changed my mind about going elsewhere for grad school I could show up whenever and they’d find funding for me), as is my current department (my group’s had numerous undergrads go through as grads).</p>
<p>Personally, I’d recommend against doing it because you really need to be exposed to different styles of departments, research ideas, and need to learn how to adapt to new environments. The people I know that have stayed at the same place for undergrad & grad seem to have a more difficult time critically looking at their education and seeing what was good and what was bad about their programs.</p>