You are doing the best you can with your busy and blended life.
Please, please, please...let the teacher and school take care of the punishments at school. When he gets home...let home...be home. Sure, talk to him about school. Talk about the "2" and that you know he can do better and you expect him to do better. Have him come up with ways he can "tune out" other kids when they are talking. Act it out with him. Ask him what he can do to not be distracted...don't just tell him what to do.
He is young, he is a boy, and it sounds like there is ALOT going on at home. Not sure where dad is...but I know I went through a lot of internal pain when my parents split and then my parents moved on and started new families. It is SOOOOO hard on kids.
Please relax and focus on his past record of great "4" scores and being the "go to kid". The year is new...he is adjusting to a new teacher,classmates,grade and class rules. And maybe adjusting to a new blended family??
Keep loving him and spending time with him. But, I can't over emphasize enough to let the school take care of the discipline for things that happen at school.
Oh...and he is so young. He is not going to give you a reason he misbehaves..that is ridiculous. He can't formulate a psycho analysis in his little immature mind that he is acting out because he feels lonely,sad,scared,nervous etc. Kids will act out to get attention..whether it is negative or positive. They act out to get noticed. They act out for many reasons they don't understand.
Try using a behavior chart with the reward being time with YOU..not a toy.
Good luck and best wishes!!
***I need to add this after seeing a post above. I too was a teacher before my kids came along. I didn't expect parents to punish my students at their own home. I would make them aware of the issue at school and expect them to talk to their child. But never punish. We are not talking about serious offenses in class. We are talking about an impulsive little boy who is on the fence gifted and going through some tough situations at home with divorce and now blending families.
I "retired" from teaching once my first child came along. Now all of them are in school. Grade school to middle school. My kids' teachers rave about what well behaved kids we have and ask what we did to nurture their good behavior. We reward good behavior and let natural consequences follow the poor choices. We also do not take the credit alone...our children are made up of so many life experiences.
Our oldest son had an amazing 4th grade teacher that told me something I will NEVER forget and boy has it helped. She said "make your home a place of refuge for your children. Let me be the teacher and discipline him in the classroom. Then YOU be the one he can come home to and confide in without fear of punishment regarding school. Talk it out..let him relax at home. Because Mom...in a few years he will be in middle school and he needs to have a good relationship with you. "
I can tell you this struck a cord with me. We applied her words of wisdom to how we reacted to his teetering math grades and not finishing homework. We loved him through it. Talked to him about trying his best and made his favorite dinner when he got a decent grade on a Math test.
You know what?? He tried so hard for the end result of a good grade, our approval and spaghtetti dinner..not in fear of a punishment. Now fast forward...that kid is going into 8th grade, on Honor Roll, received a music scholarship already, and heading off to Japan as an exchange student. He willingly takes Honor's courses with homework assignments over the summer. He talks to us freely about questions regarding sex,masturbation,girls,poor choices his friends are making etc. The open communication is sooooo much more important at this stage than giving a punishment after receiving a note saying he was talking to his neighbor in Math class.*****