When you have inept middle managers the first people to blame are unions?

Okay so over at Heritage I read this:

As Feigenbaum noted in his ruling, according to the school district’s union agreement, if a probationary teacher receives negative reviews after both years of his or her trial period, the school district can dismiss that teacher. While the 75 dismissed teachers received negative reviews during their first year, and principal reports from the second year indicate poor performance–tardiness, unprofessional behavior, “rude and aggressive” demeanor, and so forth–because the teachers did not receive sufficient written explanations for their tardiness, D.C. Public Schools are being faulted.

D.C.’s situation is a prime example of the struggles leaders face today–as a result of collective bargaining agreements and entrenched policies– that make it nearly impossible to ensure the quality of teachers in their schools.

Now the post was titled: Unions at It Again: D.C. Being Made to Hire Back Fired Teachers

So let me get this straight?  Middle management can't properly discipline workers and unions are to blame?