Right in the first season of PLL I was thinking when they were at ali's funeral why was ezra there? He never taught her or knew her? And he always seems to know everything that's going on eg;Hanna's mum going to jail, and Emily about the car going threw her house. Also when ezra was talking to Emily last episode about the car thing going threw her house he kept asking questions like "do you know who did it, etc.. And you can tell by his face when he was speaking to her how guilty he looked ?!
It would have been public knowledge on both of those things, however even if it wasn't Hanna would have had to tell the principal about it, to explain why she was off school, the principal would have to tell all the teachers that taught her, and Ezra taught her. Being a small town, the news of a car being driven into Emily's house would have spread quickly, it would have been pretty hard to hide. I don't really have an argument for the 'guilty look' but really he could have just felt bad for her. And awkward because he was with Aria, and he knows it's no longer his business.