"His brothers saw that it was he whom their father loved most of all his brothers so they hated him." (Bereishit 37:4) The normal understanding is that the brothers hated Yosef because their father Yaakov preferred him and loved him more than all the other sons. In fact, Chazal provide educational guidance as a lesson to parents from this parsha (Shabbat 10b):

A person should never differentiate one child of his from the other children. On account of the weight of two selahs of fine cloth (the ketonet pasim) that Yaakov gave Yosef more than the other children, his brothers became jealous of him, one thing led to another, and our ancestors descended to Egypt.

An awesome lesson and an awesome punishment! The Rambam (Hil. Nachalot 6:13) similarly rules: The Sages commanded that a person should not differentiate one child of his from the other children during his lifetime, even in something small, so that they will not come to competition and jealousy.

The Ktav Sofer, however, provides a novel and deep interpretation, which goes more to the roots of this educational portion. It says, "Yosef would bring evil reports about them to his father." (Bereishit 37:2) Chazal teach that he told lashon hara about them that they were belittling the sons of the maidservants (Bilha and Zilpah). I.e., this represents a slight towards the father, since also the sons of the maidservants are the sons of the father, and deserving of honor. Therefore, "Yosef would bring evil reports about them to his father" – on account of their father. Yosef's brothers accepted his rebuke on this matter, and did not hate him because of these words.

However, when they saw that Yaakov preferred Yosef amongst all his brothers on account of his mother, Rachel, they understood that the love is dependent on the mother. If so, they returned to their position that it is acceptable to belittle the sons of the maidservants due to their mothers' stature. This is what it says, "His brothers saw that it was he whom their father loved most of all his brothers," and therefore, "they hated him" – retroactively about the lashon hara that he had spoken about them! Now they received justification for their position, from Yaakov's attitude to his son, the son of the beloved mother – Rachel.

The deep lesson from this explanation of the Ktav Sofer is that we must relate equally to all the children not only in material aspects (clothes, toys, food portions, etc.) The parents must recognize that a word or world view of theirs that implies legimitization for a negative phenomenon – leads to negative behavior on the part of the children and in their world view. Yaakov's children conclude a false "world view" from Yaakov's attitude towards Yosef.

We learn great fundamentals of education from this point. For example, parents and educators must be careful not to talk against godolei Yisrael, of any kind, with belittling words. The children and students who are listening do not know to differentiate between a disagreement for the sake of heaven, which is legitimate, and the need to maintain the proper attitude towards the Torah and its bearers, and the results are liable to be disastrous, G-d forbid... Let us love all of our children and all of our students. Let us honor and revere all the bearers of Torah, and we will see, with G-d's help, blessing in our educational toil.