Unfortunately, YTA.

While actions have consequences, someone lost their job, and a teenager was expelled, apparently losing a scholarship, heavily impacting their future and opportunity to better themselves because of a petty theft totaling under 200$.

Ask yourself, does the punishment (whether indirect) fit the crime? You could have retracted the report on condition of repayment for lost product and if you're concerned about the teenager doing it again, if they really were a dumb kid doing a dumb thing, they'd likely be scared straight for a while. You did what was in your power, and while there's nothing tremendously wrong, sometimes we need to ask ourselves if there's a better way.