A Friend's comment-

 A friend's comment on teacher evaluations:

 

While teacher evaluations may on their face seem REALLY hard to do, keep in mind that performance reviews are commonplace in the private sector, and despite shortcomings, are used by businesses everywhere, every day to reward their talented employees and improve or get rid of their ineffective employees.  

My point is that I think the SOLE reason teacher evaluation systems are ostensibly difficult to achieve is the unions.  In a sane world (i.e., that which does not operate under a government monopoly), teacher evaluations would not be a problem at all.