Helianthus, DD5 is grade-skipped and before the skip, she too was exhibiting some of the behavior issues you mention and only at home. Here are some ideas that I am hoping can help you.
1. Is K mandatory in your state? If yes, is it part-time or full-time? If not mandatory or only P/t is required, maybe you could keep him in school for K for half day and either keep him at home (with a parent or another care giver). I did this-DD was in school for only 3.5 days and stayed home with me for 1.5 days. I had to cut my hours at work so there was a financial loss, but it was totally worth it.
2. Is the workload, especially writing, too much at K level and is this causing your child to not like school? If yes, maybe you can talk to the teacher and reduce mind-numbing writing work. DD had this issue and the teachers accommodated and lo and behold, now writing is her hobby. She just needed time.
3. When child is in good mood at home, sit down and try to ask him what is bothering him about school and what he likes about school. Ask him what would his ideal school look like. Even though he is barely 5, you will be surprised at how good these kids are at solving their own problems. Again, this technique worked for me so hoping it does for you too.
4. If there are any mixed-age, mixed-grade play based schools in your area,I would look into it as an option for this year and next. DD is at such a school and very content both because she has a wide variety or ages/maturity levels to find friends within and her academic needs are being met suitably.
Finally, if your kid is 2-3 years above grade level, I think grade skip is a good way to at least meet some of their needs. So, IMHO, undoing the skip does not seem like a good option.
All the best with your decision!
