I'm not really the go-to-guy when it comes to this sort of thing, but as far as I know, either of two strategies can be used to achieve high scores on Hill Top Act 1 with Knuckles. The first is a rock breaking strategy, which is allegedly similar to the one that RPGnutter uses in
this video with Sonic. However, Flying Fox has recently conceived another Knuckles strategy (
here's a video of it) that takes advantage of a Rexon (one of the pink plesiosaur-like creatures in the lava), which renders the rock breaking strategy obsolete. Sorry I can't provide you with any more info, but if you have any further questions or concerns hopefully some of the more experienced players can post some advice, and the chatroom is also a good place to ask about this kind of stuff.
(Also, ninja'd by SonicBoom737, but you still get my drift. :P)