It would be prudent to arrange an evaluation with a pediatric mental health professional for the purpose of considering whether the behaviors your son is displaying are secondary to am emotional disorder like depression. At the same time, the clinician can guide you re: behavior management. For a start re: behavior, read Lynn Clark's book SOS Help for Parents (see www.sosprograms.com).
My son is 10. I guess I didn't give him any choice for getting the hair cut then because his hair is messy from my point of view. Plus, I noticed he never sits straight, stands straight and talks to people with eye contact. He's in the GT public school ES program and used to be 2 grades ahead. After transferring from private school 4 years ago to public school, his grade is gradually dropping from A's to C's. He shows no motivation and stay low pass to all school subject. He seems only interested playing video games, watching TV and fighting with his younger brother. Worse is his anger and bad attitude toward to parents. I don't know what did I do wrong or when did I do wrong. Please help!
How old is your son? Was his behavior out of character for him when he refused your direction about getting his hair cut? Is he generally oppositional or defiant? In general, such a comment, uttered in anger, is not outside the norm. It reflects anger that is generated by a feeling of powerlessness. It is not uttered with an intention of harming you. My guess is that you could have gone about this in a more thoughtful manner, but admittedly I am only assuming that. Perhaps you were left with no choice other than to literally drag him into the shop. If you would describe the situation with more detail I'll be glad to comment further.