Originally Posted by Lovemydd
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!

Thanks for the questions and advice! K is not mandatory (I believe you don't have to be in school until age 7), but DH and I both work (and cutting back isn't an option given what we do) and there is no extended family around to help out.

I've been surprised at the emphasis on writing, which his teacher insists is just not developmentally appropriate. But our state adopted Common Core, so she's stuck teaching writing. We can ask about easing up on it; I think that may be a good idea. But I've also heard that first grade is writing-intensive, so I'm not sure if it would help him long-term or not.

His teachers commented that he was visibly towards the end of the day, so now they're offering him a 20-minute rest (in a cozy corner in the gifted teacher's room; he can choose to read if he wants). Not sure yet if that's helping, but we'll hear from the teachers in a few weeks.

We've definitely tried #3. Mostly I get answers like, "I want to send all my friends [classmates] in a rocket to the moon and never see them again." Or "The only thing that would make school better is having you there all day." (So yes, HK nailed it on that one.)

For #4, we are looking at a Montessori nearby. There are a few that are free (charter schools), and one that would be roughly as expensive as the gifted school.

It's so hard to know! Someone tell me my kid will be okay and I'm not damaging him for life by making him go to kindergarten. (Okay, that sounds ridiculous, I know! But I do worry.)