While some private schools do a better job of informing students, the mandate of public schools (as pointed out) is more general (or specific, depending on how you count).

Things get a little better in college, but even there your readings are very directed.

You are correct, IMO, to conclude that the only way to really get informed about stuff is teach yourself.  All the smart people I know are pretty much self-taught in almost everything.

For me, the trick is to find something that interests me.  I can't just tell myself "well, time to learn about the geology of Africa".  That's too much like self-imposed school, and bores me to tears.

Instead, wait for inspiration to strike, and place yourself in a position where you are exposed to potential inspiration.  Read magazines - Newsweek, Economist, Popular Mechanics, Psychology Today.  Trawl the internet.  Go to news sites, but don't just read the headlines - click on all the links, and let yourself get carried from site to site.  You can learn a lot that way.  The Economist and the Wall Street Journal in particular are just packed with information, although it can be a bit dense at times.

And, most importantly, when something grabs you, follow up on it.  If you keep hearing about "Darfur" and are wondering what it is - go find out!  Google Darfur, Wiki Darfur, Amazon Darfur (you don't have to buy from Amazon - I use it like a giant library search engine).

And don't get discouraged.  When you are starting in on a new subject, you are bound to be confused by everything you read.  Don't let that stop you - just accept that you don't understand it yet, and keep reading.  If you only understand 20% of what you read, you are still ahead of most people.

I could tell you some books to read, but unless the subjects are of interest to you, you will hate it.  Learning has to be fun, otherwise you won't.

That said - here are some books I read recently that are fairly easy to read.  If the subject matters interest you, give it a go:

 - A Brief History of Time, Stephen Hawking (physics, big bang, black holes, etc.  Still dense, but the best physics for dummies book I know)

 - Evolution, Carl Zimmer (evolution - duh - written in conjunction with a PBS series on the subject.  Very easy to read.  Certainly not a treatise for professors, but a very good place to start on the subject)

 - The Communist Manifesto, Karl Marx (communism and political theory.  It's a slow read, but it is very short, so you can take your time.  Make sure to get a version with a long introduction/background - the historical context of the document is as important as the text itself)

But mainly I would recommend the internet and magazines.  The amount of fairly indepth information available by those sources is staggering, if you take the time to go find it.  At this point most of my daily information comes from the internet and The Economist.  And the Daily Show.

Another source to consider is NPR.  Any issues of political bias aside, NPR is still, TMK, the best information source on the FM dial.  Listen during drive times - 7-9 am, 5-7 pm, give or take.  They almost always have some type of quasi-political/current events discussion.  Again, your purpose here is not to agree or disagree, but to learn.  Ignore the callers - they are idiots - but listen to the guests.  And then go research whatever caught your fancy.  Maybe they have a thing on global warming.  Maybe you think global warming is bunk, but the guest on NPR mentioned some factoid that interested you.  Now go google it, and before you know it you will be a global warming expert.

Bottom line - expose yourself to surface information, and then hunt down details on stuff that interests you.  Not only should learning be fun - it HAS to be fun.