True

I actually didn't want to make the answer too long but I was thinking of that a little. Now we are used to elites based mostly on economic status. But over time elites have been hereditary aristocracy, military leaders, religious leaders, and so on; and now I could even include politics based elites who didn't come from these groups (I mentioned Maduro in another thread. Ocasio Cortez is another example. There are more). Many times these didn't intersect completely. For instance in Dharmic societies religious elites many times were privileged socially but economically rather poor. In the West the very rich were not always the most important people especially when aristocracy and church carried more real power. In Classical Islam the three sorts of elite could change over generations from one sort to the other and the latter two provided some social mobility. Chinese bureaucracy did too to some degree. It's well known that for a time in Classical Rome you lived better as a rich plebeian than a poor patrician, and even as a house slave to someone very rich of either hereditary class.

And this is only about general trends. As you point out, sectors within each may be less privileged. Children have historically not had the social clout of their parents. Societies with entrenched aristocracies have witnessed children being in arranged marriages for keeping the hereditary class a closed shop.

What is different with children and the more so in modern societies is that they are intently disenfranchised even when they are born into an economic or aristocratic upper social group. In that sense I may not be as "children ist" as OP but I definitely perceive the problem and have seen it have ill consequences for children; sometimes with long term effects.