Help- My Kindergartener Has Absolutely No Desire to Do His Work at School

Welp Moms, I am at a loss here and thought I'd turn to you guys for some advice. I'm hoping someone else out there has experienced this problem before with their own child. My oldest son is 5 (with a late May bday) and in Kinder. He had a rough start at the beginning of the year, but finally seemed to settle in quite nicely. He had a slight issue of not getting his work done in the time allotted- but not anything that was a cause of concern to his teacher. Whom by the way, I must add, has been teaching Kinder for 46 years! She is strict (which my husband and I have no problem with), but after many observations of her around the children it is apparent she truly loves both them and her job. Once again before the break we addressed this issue with him and it seemed to become a non issue rather quickly. HOWEVER, here we are back to the grindstone and my little guy can't get with the program. Every since we have returned to school he has come home with a note and a couple of assignments (i.e. handwriting,cutting, coloring) that he was unable to complete during school. Many of the notes say that she had given him 2 days to complete the task but still to no avail! When I ask her what he's doing during independent work time she tells me he's fidgeting, walking around, laying on the floor (ALL the things we see at the dinner table)looking around, talking, staring off, etc., etc. When he's redirected he focuses for a couple of seconds and then starts messing around again. She said she's put him in a "private office" (where the teacher puts folders around him during work so he's able to focus better) but that hasn't helped. So far all of her tricks at school are not helping his bad work habits. Now for things on the homefront. At the beginning of his downslide a couple of weeks ago we approached the issue with positive reinforcement- i.e. sticker chart, get to pick the family activity on the weekend. Then as we quickly saw that was not working we downshifted into negative reinforcement. Taking away privileges, beloved Christmas toys, still nothing. Oh yeah, we can't take away T.V. time or video games bc we don't really do either of them- (well they do get a couple of hours on the weekend but not enough to be a big deal if he doesn't get those hours) I know we all have little geniuses out there, and I in no way think my child is the smartest cookie in the jar, but academically (both math/reading) he is functioning on at least one (if not more) grade level higher. I have been an elementary teacher for several years before I decided to be a full time mom so I think my working with him is the reason for his higher academic thinking. I'm also 95% sure he doesn't have an attention problem- I've kept an eye out for that for the last couple of years and other than the issue at hand he really doesn't show any other signs. When I ask him what's going on and why isn't he completing his work, he swears he tries but he just runs out of time (which is not what his teacher is telling me). He claims he's just to slow- However, when he comes home with the work he gets an entire days worth of work done in under 10 minutes. I just don't know how to tackle this problem, I'm at my wits end and am frightened that he is developing really bad work habits which will definitely become a HUGE problem as he progresses through school. I have a conference scheduled with his teacher for late next week but like to bring some different ideas to the table since we have both exhausted most of the ones we know of. I also wanted to add that when briefly talking to the teacher, I asked her several times if she thought he had an attention problem and she agreed with me that she really didn't think so- She did add, however, that he is a younger kinder and a lot is immaturity. Okay moms, throw me some advice, suggestions on how to tackle this;-)