[Tango-L] How to break couples who do not want to change partners.

[Igor Polk]

Ok, no one knows how to grow a good ( I mean excellent ! ) man-dancer.
GOOD !

Now, much more practical question.

When one has 4 couples who do not change partners per, say, other 6-7
couples, it is a real disaster. 
These people just dump the energy ( not to speak that they needed it most ).
Especially if the class is more difficult than average, and if there are
some extra women.

What to do with it?

I am ready to tell them to leave if they do not start to change partners.

I already used all persuasion power I know of, telling stories that it is
good for them, bla-bla-bla, and for forth..

Can anyone help me with an advice how it works in practice?

Note: all students are of the same level. Actually those who change are
better, and they do not mind practicing with less advanced stubborn
not-changing students.

Or may be I am wrong? Should I dump those who are without a partner?

Igor Polk