Step 1: Propose an UML assignment to your students (it doesn’t need to be very difficult, if the group is big enough you are guaranteed to have some that are lazy and rich enough at the same time)
Step 2: Wait some hours
Step 3: Look for a job post consisting in solving your assignment in any of the freelance sites (see this one as a representative example, as you can see, they don’t even try to disguise the fact they are happy to pay to solve their academic exercise).
Step 4: Bid for the project claiming to have great UML skills. You could even mention you’re especially good in the academic domain!!
Step 5: Take the money and send them the solution with some cleverly hidden mistake
Step 6: Check who is the stupid student that paid you and make him repeat your course next year
(Possible) Step 7: If the student is stupid enough, you may be even able to repeat the process with him/her again!!!
(and now, if you want a serious recipe on how to teach UML & MDE you can check this presentation)