Ad valorem is a stupid and medieval method of assessment.
It is antiquated and is completely unsuitable for our modern society. It arose from a medieval practice in which the income of estates or property, was taxed. It was a way of taxing the productivity of land and holdings. That's all. It was, in essence, an "income" tax, since people had no other real way to generate income except from real estate. You either farmed it, fished it, hunted it, or raised animals on it. And that is what ad valorem tax was applied to, the "value' of the estate, meaning what it produce in income, on an annual basis.
In England, when you spoke of the propertied class, a phrase of speech was "She's worth 300 pounds a year". Well what that means is that her estate, or portion of an estate, produced 300 pounds in income.
So, for us moderns, who do not derive any income from our homes (unless we are a landlord and rent them out, in which case the income is taxed by the income tax ), an ad valorem tax is wholly inappropriate.
Why? Because the price of the house has zero relationship to the costs that are imposed by it on the infrastructure of municipal services. The price is completely arbitrary. It doesn't tell you how many people live in the house, or anything about the services they consume. It is a meaningless number.
So real tax reform needs to eliminate this medieval practice of ad valorem taxation, and instead focus of providing a fair and equitable way to assess taxes - one way would be to establish some baseline level of services to which every similar parcel (iea SFR is similar to all other SFRs, a MFR is similar to other MFRs), is "entitled". Thus all parcels are taxed the same way. This is how, for example, the sewer connection fees are assessed. They don't care if you have chronic diarrhea or if you make all your bowel movements at the gym and never flush the toilet at your house.
In any case, the fair way is to say "Look, society has a vested interest in providing "free" public school education to citizens, but there has to be some kind of limit on what is reasonable. Is it really reasonable to ask society to pay for schooling 10 kids if you can't keep your reproductive organs under control?"
In this kind of a scenario, you'd have a baseline. A good baseline for children is two, because two is a socially and globally responsible number of children - it is the "replacement" value - so it helps keep the population steady or better yet to shrink it slowly.
So you'd get "free" education for two kids, but additional ones are at your own expense. That kind of thing. Why should society subsidize your children beyond a socially responsible number?
That makes no sense and is certainly not "fair" to childless people or people with one or two kids. Even childless people benefit from a reasonable level of procreation, because those replacement people ensure that services can continue to be delivered as those replacement humans grow up and enter the workforce.
Sure, maybe you're childless, but if nobody produced new humans, all the people who service you would die or retire. That clearly is not sustainable.
Sorry for the long post. I really meant to simply illustrate how obviously unfit and unfair "ad valorem" taxation is, and how there are other ways of looking at taxation in a much more equitable and reasonable fashion.