It's always the parent's fault isn't it? In my ds's case we would never have asked for him to be assessed as we find he fine if slightly highly strung at home. He does what is asked of him, though he may need a reminder or two and although he can get angry and upset more easily than some other children, we manage that and he seems to thrive at home the vast majority of the time. All of our family think he is fine if a bit quirky, none of them have ever said they don't want ot look after him or that he is any more difficult than other children in the family.
It is at school where is behaviour is almost unmanageable - He has a dedicated 1:1 TA for 20 hour a week, which is almost unheard of and we have just received his statement o SEN, one of only around 3% of children nationwide!. In this case I assume it is the our fault because we let him do as he wants at home and haven't prepared him adequately for school 
Parents really cannot win. if the child misbehaves at home but not school, the parents are to blame and are in denial as to how they parent.
If the child misbehaves at school but not at school, it is because the parents are also in denial and don't have high enough expecations and/or lying.
Having got all thst off my chest however, I would actually agree that what the OP describes seems normal to me. Her ds may well be worried about school or a number of other things.
I personally would try a combination of clear expectations and als asking her ds about any specific incident (later when he is calm), not why he did something but try and find out her ds's view of it.
The best way to do that is to ask questions about what happenedm but not too much about feelings or motications which just tends to confuse most children.
Something Like "I noticed yesterday that you were really angry when...,tell me what happened" Then ask questions to try and re-create what happened from your ds's point of view. Factual questions Questions like "what happened then, who was there, what did they say etc. "
When I have done this with my ds I have opten ben quite surprised at what his view of things were and what the problem was. Sometimes it was nothing at all like my view of the events.