If the story is accurate, it was on the clock. 

That's not exactly right.

Unless the proper authority authorized it.

It would seem to me that the proper authority would be the superintendent.  

It was her car.  Therefore, it would seem to be plausible to think that she authorized it.

If that is the case, then I do not see where there is a "theft of services" issue here to even bring up.

If the superintendent did not have proper authority to allow the shop to be used, then that sounds like an issue between the superintendent and her board of education. 

The only problem with that is that the board of education was not even consulted to determine if they authorized the action, or if they considered it to be within the authority of the superintendent to authorize it. 

Big picture here...the article states that the mechanic makes $30,000 per year.  If you use 2000 hours per year, that is $15 per hour.  3 hours makes $45 we are making a case out of here (and that is assuming that the mechanic was in fact on the clock at the time).... with no complaint by the supposed victimized party, which would be the board.

Until such time as I see some evidence otherwise, I'm going to say abuse of power by sheriff, county attorney, and/or the Mark Angel character for the purpose of advancing some personal agenda or grudge.