Is it legal to post a sign in a workplace of employees who made mistakes?

It has the employee's name written down, what they made a mistake on and how much the mistake cost the company.

Yes, butt is isn't a very good management practice.

This is rude and crude way of trying to motivate employees unstead of training them in the correct way of doing things.

When I recruit a new person, part of my promise to them is that I will train them to be successful.

Now, I'm in direct sales so it's different because I am teaching people how to sell an make money, not how to do a menial job for small wages but thats where almost everyone starts out, as a menial worker and unfortunately that's where you will usually meet the manager who won't do their job correctly. These stores are usually where they have the highest turnover and often pay a lower wage than a comparable store.

Unless the poor performance review is posted in a public place you can't do anything about it legally.