There is always the chance that the misdemeanor conviction for theft could have a negative effect upon your desired career as a pre-school teacher in that the conviction may very well pop up in a back ground check of you.However, if you are able to get the conviction expunged, there is a good chance that the conviction will not appear on any background check and if so, there should be no fall out as to you concerning your career plans.I suggest that you consult with a criminal defense attorney about the expungement and the conviction upon your desired career path.Good luck.