OP here to address a few follow up questions.
It is absolutely a financial consideration first and foremost for me. We are maxing out elective contributions to 401 (k)s and funding 529 acct, but we still have a mortgage & HELOC. Emergency funds are not as well funded as they should be and we haven't done roth conversions. Spouse makes around 50k. My income is variable, but usually on the low side of 100-200k.
DC comes first, always. If there were some special needs reason to pay for private school, we'd make it happen. DC is just a toddler, so of course things can change, but as far as I can tell, is a developmentally normal kiddo. Spouse thinks DC is brilliant,

and will therefore need the private school experience.
We are one and done (at least there will be no more children from me!) So sibling equity not an issue.
We certainly did talk about money and kids and other important topics before we got married, but we married young and views evolve over time. Sending kids to private school is absolutely a status thing and would give spouse opportunity to hob nob with the SE class of our youth, which unfortunately, we are not in.
Divorce is not imminent. We are pretty happy. I'm just cranky because my in laws are in town for another week and as a child of divorced parents, it colors my perception of well, many things, including big financial commitments.
I think what irks me the most is that spouse thinks nothing of my laboring for an extra 7-10 years in order to pay for private school, even calling me lazy! Sorry, but I don't actually enjoy working. Especially not to pay for an expensive luxury.