Before going to Mars I would like a decent school on my street.
If you look at a graph of average inflation adjusted spending per student at public schools it's just a monotonically increasing line from the end of WWII until today, it just goes up, and up, and up.
But does average student educational outcome match such graphs? Not in the least. The problem is that the incentives are all wrong and the money keeps getting funneled to the wrong people. The ratio of administrative staff to students has grown and grown. The biggest influence that active parents have had on schools over the past few decades has not been on increasing educational quality but on driving administrative policy through excessive litigation. Increasingly K-12 public schools are little more than prisons where kids do busy work and if they're lucky the smart ones learn how to teach themselves and most of the rest pick up enough of the basics through repetition or osmosis.
Don't expect the results to change until the system changes.
Figure there are 50million kids in public schools and we spend 12k a year per student. So if we spent $11.6k a year per student we could more than double NASA's budget. So a 4% school budget cut vs a 100% NASA budget increase. I honestly wonder what direction educational attainment would go if we made that trade.
I wouldn't be surprised if it went up.
Seriously, there's tons of more pressing issues back here on Earth, ranging from real, social one like inequity and discrimination, technical/political ones like the ever growing piles of garbage all over the place, healthcare, climate change and mass extinctions, and say, taking care of that whole cycle of oppression and bloodshed that has been going on for a while now (not that it'll go away, but we're pretty fucking screwed if we don't come up with something which will leave most people content).
None of those problems will go away if we send little men on tin cans to space, and in fact, I can think of very little problems that will be solved by that. We're a long way from escaping the mess which we have created here on Earth, and wherever we go we'll do it again, and that's being optimistic in saying that we will actually get a self-sustaining Homo Sapiens population off the planet before our shit catches up with us and we're actually forced to do nothing but deal with the consequences.
All that said - perhaps... perhaps... Perhaps the minerals and compounds needed to survive as a species are elsewhere in our solar system.
Not only that, but more than we could at this point imagine using in a long long time, and an inexhaustible supply of energy. I find it hard to believe that these resources wouldn't help us just a little with the seemingly intractable social problems. Those very often boil down to arguments over limited resources in the end.
In fact, I can't think of a major world conflict or problem that isn't at its root about the allocation of resources, and it's all there for us, right above our heads.
[1] Not just in hindsight, at the beginning for many people. [2] It feels odd to me to write trillion and actually mean trillion and not "some really big number".
Health care research is cute and all, but we don't really have a system that lets it benefit the vast majority of people, yeah? We are doing our damnedest to wall off the research that comes off of it, yeah? We are setting ourselves up for unrealistic expectations and a fantasy world where our loved ones never die, yeah? That's not worth spending money on.
Education cost is not the point--other replies covered that better than I can.
Solving world hunger? You mean, feeding people who can't feed themselves while we force our own poor into shitty lifestyles from eating junk food, yeah? Giving food to dictatorships in hopes that they, oh lawdy, don't develop nukes? Giving GM crops and their associated IP to fuckwads like Monsanto so that they can get a stranglehold on the food supply, yeah?
Space is the least harmful of places we've tried to make policy.
If we abandon grand visions, I honestly don't care if people are educated or not.