My son has started grade r this year. his behaviour has changed dramtically since last year in preschool.he refuses to listen to the teacher and he gets emotional when repremanted.my 9yr old boy is fine. what to you recomend? dr or psychologist?

Likely both: The situation is suggestive of learning issue/confusion in the kid. I would start with his regular doc who can rule out any medical/physical issue that would impair learning. S/he would likely know who in your region is available to assess a child with these problems. There may be a need for both to work with the kid over time.

see PCP 1st: It sounds like he might have a sensory processing disorder, be sure that is considered, a sensory integration evaluation is a specialized occupational therapy eval. Best Wishes