At a very early age children learn the history of the world and the Jews through the enthralling stories found in many varied sources.
They learn that the world was created in six days; that Avraham knocked down the idols in his father's store; that Hashem told Avraham Lech Lecha and Avraham and Sarah traveled away from their homeland; that Issac married Rivka at the age of three; etc.
The problem with teaching in this way is, in my view, children don't differentiate text based stories and Midrashim. This may no seem to be a problem on the surface, however just from the list above we have a two-fold problem.
First, when the student begins to be able to read the chumash on their own some famed and loved stories do not appear even as the student spends hours searching and becoming discouraged at the text and his/her teachers. I have adult friends who still remember being very confused that Avraham's father's idol shop appears nowhere in the text.
Second, several Midrashim can be found on certain issues, including that of how old Rivka was when she got married, so once the student can reconcile him/herself to the fact that his/her teacher has some how mixed everything up in his/her head (if they can reconcile themselves) the student now has to deal with the fact that he/she was taught only one of many possible stories and therefore needs to explore why the teacher chose that one to teach and how will he/she now be able to reconcile all the differences of the rabbis with the over riding bias that the teacher gave him or her at such an early age.
Therefore, when should we be teaching the differences between Midrash and Text and what can be found in each? How do we help both students and teachers with how to incorporate both into teaching without causing students undo difficulty while still receiving a complete Jewish education.