How is that a 'downside'? Being able to fire incompetent people is an UPSIDE!
I'd say it's a downside because people can be fired with flimsy evidence or without being charged with any wrong doing. In this case, it appears from the principal's own statement that these teachers messed up. But in other cases, it's not so good. For example, students can lie and accuse teachers of misconduct - and the teacher can be fired with no redress. In that case, it's bad.