Quote Originally Posted by basurero
Я проучу уродливого мальчика, который украл у меня бумажник.

I will teach him a lesson????
Correct.
Проучить here - to teach a lesson

The difference between Chuvak's suggestion and this is in the fact that Chuvak intends just to punish while проучить = to punish in such a manner that the said thief would learn not to steal anymore or regret it bitterly.
Of course you can beat him but to me there is a difference between проучить (to teach a lesson) and наказать (to punish).

You can also say:
Я отучу его воровать.
Отучивать = to break of a habbit, to disaccustom.

Or, like Chuvak said:
Я отобью у него охоту воровать.
(I'll beat the stealing out of him)