<p>It probably will depend on how you write the cover letter. I think (in contrast to your guidance counselor) that many teachers appreciate it. Just phrase it as a request and in saying why you selected that teacher you can provide the examples you would like highlighted in the recommendation. For example: I am asking you to write this rec because your class has inspired me to pursue… especially when we did…and I designed the lab for … and you allowed me to teach the class about… You fill in the blanks. But phrasing it that way is complimentary and appreciative of the teacher and triggers his or her memory.</p>