Unless you're significantly wealthier than your neighbors, most likely the public school for their grade level closest to your home, which you picked in large part for the quality of the schools.
And who is, in the end, the parent usually taking children to school and picking them up, and dashing over to pick them up if they get sick or injured?
The mothers.
For younger children, daycare arrangements were made based on where the primary caregiver (usually, mother) plans to work.
When that plan all of the sudden becomes "compulsory hybrid", you can't just split the kid's time between two daycares - in a lot of places, just getting that first slot was hard and expensive enough.
There's the simple fact that the daycare near your house might not open early enough or stay open late enough to accomodate your commute. Plus, I kind of want to do more with my little kid during the week than get him ready for daycare and get him ready for bed.
These aren't all the reasons that RTO pushes young (and young-ish) women out of the workforce, but are just the first examples that came to my mind.
If it were easier to fall back to part time but stay in tech for a few years, it wouldn't be as big a deal.