Hello!
 
As a mom with kids in elementary school, there's something that feels "fishy" here. It's surprising to me that your son would get sent to the Principal's office for sitting on his knees. Especially if he's an otherwise good student as you indicated. At my kids' school, trips to the principal are reserved for much more serious violations (hitting another child, repeatedly disrupting the class, being disrespectful to a teacher, etc)
 
Are you hearing about the punishment only from your son or also from the teacher? If your son is making the reports about getting sent to the Principal's office it's possible that he's not understanding exactly why he's being sent there. (And unfortunately, it's also possible that he knows he's being sent for something else but not being totally honest with you about it).
 
I would ask for a meeting or phone call with the teacher to talk about this situation. If, as I suggested above, he doesn't understand why he's being sent to the office, he'll never be able to improve his behavior and get out of that pattern. If you clear that up with her you can then clear it up with him and help get him going down a better path.
 
If she's really sending him to the office for sitting on his knees, it seems like the two of you (or three if you include your son in the conversation) could come up with a more effective strategy to help keep him on his bottom. Maybe a positive reinforcement chart where he could earn a star for each time he stays seated during group time. Then he could earn a reward from you or from her every time he earns 3 or 5 stars. Or maybe he could have a new seat on the carpet that allows him to see everything without popping up on his knees.
 
And, if you learn that your son hasn't been being honest with you about why he's being sent to the office, there's an opportunity for you to open up a new conversation about his behavior and the importance of telling you the truth.
 
Good luck!
 
Kat

Is your child able to sit on his bottom as required?  Some children cannot sit flat in the "criss cross, applesauce" position due to discomfort in the low back or hips.  Make sure he can sit flat.  Other children prefer to sit on their knees because they have difficulties with sitting balance.  Make sure that it is "not being able to see" that is keeping your child from sitting as his teacher desires.

As a second grade teacher, I have the philosophy that as long as a child is learning and not distracting other students, I don't really care if they sit on their bottom or their knees.  That being said, I'm a young teacher and perhaps your son's teacher is older and more accustomed to strict rules and procedures with no "wiggle" room whatsoever.  If your son tells you he can't see, then my suggestion would be to request him a seat closer to the instruction being given.
 I do however see her position in inforcing the procedure of sitting on your bottom. It sounds like other children in the class abide by the rule and without punishing your son for the infraction, she is then setting the example that it is okay to not follow the rules. Try getting him moved up closer so he can see.  The problem may correct itself.  If he is closer and can now "see" and the sitting on the knees continues, then it may be a simple behavior issue.  Good luck!

I teach first grade, have been for 8 years and it seems weird to me that she would send him to the principals office for something like that. Yes maybe she has a rule about sitting on thier buttocks but has she ever taken the time to sit and ask him why he does what he does and try to talk to you before just sending him to the principals office like he is a disruptive student. Try talking the time to organize a parent/ teacher conference to discuss this issue. You never know maybe she is just frustrated and doesn't want to deal with the issue. Make time to talk to her.

I am a teacher assistant in a kindergarten classroom.  We have this same problem with sum of our students.  Even though it seems like a tidious thing to be sent to the principals office for but it is very important.  If he is sitting on his knees, he is blocking the view of others that are behind him.  Also sitting on your bottom and hands criss crossed in the lap is an assumption that they are in a listening position.