Should writers share unpublished work?

How many of you as authors allow others to see your work before it is published or in the pipelines for publication?  I figure the answer will span the whole spectrum.  I know many artists/authors who will not permit a peek of their work, not even to talk about their books before the publication date is set.  And then there are those who won’t stop talking about their WIP and you wish they would shut up and publish it already.

Not only is that done in the arts, but also in science.  I recall as a first year graduate student we had to write a mock grant on a particular research topic for Microbiology.  My partner and I chose a relatively rare infectious pathogen and were excited when the leading person researching that pathogen was the invited speaker at a seminar.  As you would expect we inundated him with questions.  However he looked at us with suspicion and asked who we were working for.  No matter how we explained that it was just a mock exercise, he would not answer any of the questions but referred us to his already published work. 
That was quite a surprise for me and my partner because both of our mentors were always willing to share their research with the world even before it was published.  In fact, once when I asked my mentor why he shared our research before it was published despite possibility of being scooped his response was that science is supposed to be shared with the world.  And yes the end result is that someone else published the same research before us—we were scooped.

That is why I’m having a little dilemma.  I have no problem sharing my unpublished work with others as long as it is not stolen.   Two years ago, my daughter and I wrote two books in a series of books that involves children on a journey into the cell.  The book was meant to help children understand the structure and function of the cell and its organelles in a fun and exciting manner.  My daughter is now learning about the cell at school.  I realize that both her and her classmates would benefit tremendously by reading the books, however, I haven’t published it as yet.  So after agonizing over it, I sat her down and asked her if she thinks it’s a good idea to offer her teacher access to the unpublished manuscript as a resource.  After careful thought (all of ten seconds) she says it’s up to me.  The ball is now in my court.

Should I do so?  Should I not?  I’m still undecided.  Why?  Well for one, will the teacher or one of the parents of the students take the story and publish it as theirs?  Would the teacher think I’m usurping his authority in the classroom?

I have about one or two weeks to decide, but as of now I am still between two minds.  What do you think?  Should I offer the unpublished manuscript as a resource or should I let sleeping jumbie rest?  And what are some of the downsides or upsides to this decision?