I don't know the ideal compression ratios for the Aveo, but your numbers are way low. You might possibly have a warped cylinder head. You mentioned that the head was recently removed and replaced? Its quite possible that the head wasn't torqued down correctly or the gasket was installed properly. What was the reason for removing the head originally?
And your mechanic is asking you what to look for? It's time to look for a new one.
Personally, I would pull the valve cover and check the torque on each of the cylinder bolts. I would bet that the bolts wernt torqued down fully or in the correct sequence. While it is possible, I would rule out an improperly installed head gasket; most likely your car would be overheating at this point if the gasket was installed backwards.