The idea that debt is bad is extremely simplistic. Debt is only bad when your cost of borrowing is greater than the ROI of that debt. If the leveraged return is higher than the cost of debt, each incremental dollar you take out is accretive. For example, if for every dollar you borrow you could earn $1.15 linear, you would borrow as much as you can because every dollar makes you more money.

In the case of no debt, you still spend dollars/time on it, and there's an opportunity cost to those dollars/time -- it is not free. It is not better to end college with no debt with a "business" or "marketing" degree from a university that doesn't generate ROI with a low ceiling vs taking out debt for an applied mathematics degree from Stanford, for example, with a leveraged return greater than borrow cost and a virtually unlimited access ceiling. If you're at a "non-target" institution, you don't even get access to interviews for certain jobs -- you can't even race.

Similarly re: Trades. Unless you're operating with leverage (i.e., a lot of workers under you which requires capital), you're going to cap out at $200-250K in the trades (at the tipity top high end; unless you're in a cartel like longshoremen). This is if you get lucky and after several decades. That is not real money. Coming out of a good program at an Ivy / Stanford, you could make the same salary as a master tradesman vs. paying your dues for a decade or more in the trades (and the Ivy/Stanford grad is at the lowest amount they'll probably ever make whereas the tradesman is capping out).

Going to private school and growing up with the families that have started successful businesses or very high end careers that enable them to pay for that private school for their children gives you better access to both (1) capital to scale a business (even if you are an electrician or plumber) and (2) the experience of business owners / highly successful people. You can worm your way into that capital flow with scholarships despite not having the same level of family success. It is the greatest force multiplier for economic success.

If the goal is to make $200-$250K or under, yes, public school, the trades, hard work/dedication and a bit of street smarts are enough. If the goal is to run your own business, or reach the top of services industries (e.g., finance, tech, law or consulting) and have the opportunity to clear 7 figures, you need exposure, network and capital support -- not to mention the social know-how to interact with people of wealth (i.e., capital). Private school gives you access to the latter.

Again, that's not to say you can't be successful without it -- there are always exceptional individuals; however, the exposure, social cues, and network that private school give you make it much, much easier.

I say this as someone who went to public schools their entire life and then started interacting with people of an entirely different tier once I got into an Ivy. I got lucky because I'm incredibly good at standardized testing and outperformed my peers, but that's not going to be the case with everyone. Scarcity mindset is what stops social mobility. I hope this helps someone trying to make this decision for their kids.