An answer of the Rebbe relating to the cause of children going off the Derech:
In response to a letter written by the organization Nishei U’benos Chabad regarding the trouble faced with rebellious youth, and the message that they should give to the public, the Rebbe responded as follows:
Based on the words of the Rebbe Rayatz, the suffering r”l that [parents] have from the youth comes [as is evident in a number of Sefarim] as a result of leniencies in Taharas Hamishpacha and modesty. And from the positive you can understand the negative, that the Tzenius of Kimchis brought seven Kohanim Gedolim.
 Published in Mibeis Hamalchus p. 131; K’far Chabad Vol. 746