My oldest is eight and has this issue. I will also mention that my son is very bright...all of his grades are 90-100% and all of his teachers since preschool have commented on his extraordinary vocabulary. When he was only 13 months old he asked " where is my triceratops, mommy?"
It was his first grade teacher that really brought it to our attention, although, I had noticed similar examples at home that you notice. She started him on a sticker chart at school that she would keep at her desk, not in view of other students, since it was not a behavior-related problem. This was not effective. He had no idea until the end of the week, how his week went. The chart was broken into AM and PM...stickers for paying attention without staring episodes and then "X" for times when he didn't pay attention.
He is in second grade now and his teacher has a much better system. We met with him at the beginning of the year and he came up with a self-rating system that has increased his awareness of his attention/zoning out...about 2 months ago he quit doing the system all together because it is no longer an issue!!! He also used a chart that is broken into AM & PM that was kept at the teacher's desk. (I made it clear that I wanted him to be discrete when talking to my son about this...I didn't want him to feel embarrassed in front of the other kids) Everyday, when the teacher told the students to line up for lunch, he would have my son come up to his desk to quickly rate his morning 1-10, with a picture rating scale(sad face next to 1, happy face next to 10) for the following goals:
1. I followed the directions that Mr. C. gave in class.
2. I had my book open and my papers ready when Mr. C. told me to.
3. I was ready to answer Mr. C's questions when he called on me.
Mr. C wanted to know how my son thought the morning went first, and then Mr. C would give him his rating. The goal was to be between 8 & 10. Mr. C. would then do it again at the end of the day when the kids were getting their backpacks ready to go home for the day. This increased my son's awareness significantly because he had to rate himself.
I should also mention that I am a speech therapist and the "zoning out/staring episodes" scared me from a medical standpoint. I have known kids that had a petite mal seizure disorder and 1 child with a brain tumor who also "stared" into space. I went to the pediatrician at the beginning of this school year and asked for an EKG and MRI to rule out seizure activity and a tumor. I am not trying to scare you, but, for obvious reasons, it is a good idea to rule out possible contributing medical conditions. Good luck and I hope that this information helps you.