In Milwaukee, the so-called dance of the lemons occurs, where bad teachers are passed along from school to school in the hopes of minimizing their damage.
The dance of the lemons is an analogy for passing off a bitter partner. However, only lemons are dancing, so one is guaranteed to end up with another bitter partner. Although Milwaukee is not known for producing lemons, it is a common fruit known for its bitter taste. Perhaps this phrase implies that Milwaukee may have more than a few bad teachers. Although many states have some poor teachers, it is bad sign that so bad teachers needed to be traded that people started naming the practice.
This quote is published on the following website and the article was written by Blake Neff
http://dartreview.com/dartlog/2011/4/23/the-superman-cometh.html