FYI, courts don't collect money for anyone but themselves. If they grant a judgement it's up to you to collect it. I stopped going after monetary judgements when I have to evict a tenant for non payment. I've had two monetary judgements and collected very little of either of them.
Have you ever tried to collect on a judgement?
I think withholding a high school degree would be the most effective as this is not going to court. I have too many other students who deserve my time.
But anyway, pertaining to your question there are several ways to collect a judgement. You can freeze their bank account. You can get DMV records and take their car. You can garnish their wages. Some people are judgement proof.
Sadly, you should not rent to people who have nothing to lose if you plan on staying in business. Too many people see kindness and generosity as weakness. And having someone think you are weak is the best way to find out what is really in a man's heart. The government has made it so helping people out is punished with 2-3 year eviction moratorium and very little accountability. In my area it has caused a housing crisis, lack of supply, destroyed units, and sky rocketing rents. Screen tenants hard and good luck.