Parents and Teachers – [Few tips on nurturing Children] – Imaam Ibnul Qayyim
And from that which a child is greatly in need of is that his (or her) manners are given attention; for indeed he (or she) is brought up upon the nurturing of his (or her) nurturer during childhood—be it (traits of) fury and anger, stubbornness, hastiness, being quick in following his (or her) desires, heedlessness, excitement and greed. It becomes difficult for him (or her) to break away from this in his (or her) adulthood, and thus these mannerisms become firmly grounded characteristics and personalities in him (or her). If he (or she) does not take great precaution against them, it will shame him (or her) someday. So because of this you find that many people are deviated in their manners and this occurs due to the manner in which they were brought up.
And due to this it is obligatory that when the child reaches that age in which he (or she) becomes conscious of good and bad, he (or she) is kept away from gatherings of jest and falsehood, music and listening to lewd speech, bidah and evil speech. That is because if he (or she) is accustomed to listening to these things, it becomes difficult for him (or her) to part from them in adulthood, and it becomes difficult for the one in charge of his (or her) affairs to keep him (or her) away from it—because to change one’s habits is from the most difficult of affairs and requires the person with such habits to change the nature he (or she) was nurtured upon, and to abandon one’s nature is very difficult.
[Slightly paraphrased. For further details see Tuhfatul Mawlood…page: 349-350]