So I'm a person who has two teacher's as parents (with some 60 or so years of teaching between the two of them). I have been listening to my parents talk about teacher/education things my entire life, and I'd like to think that I've at least picked up something from those many many years of conversations. I'd like to start with one important note: While there are many students/parents of students that are perfectly cool with their child and school, there is also a vast majority of them that are total idiots about things. I'm talking about the type of parent who comes in and demands that their little baby be given a passing grade three days before grades are due... despite the fact that they have a 12% in the class and have done literally nothing for the last 8 weeks but distract other students and talk in class. Now you would think that these would be quite rare, but from conversations with my parents I have learned that they are in fact quite common.
Yes, individualized learning is a wonderful thing, and is definitely something that should be done for more intelligent kids (my dad was the head of his school's gifted program for several years), but honestly it's not something that you can count on lower level kids to accomplish on their own. The reason that going to school is mandatory is because without it we end up with a fairly big chunk that would miss out on opportunities and know absolutely nothing. (And if you'd like to point out that they aren't learning much anyways, I'd note that I've seen several examples of problem students who have been turned around; students that wouldn't have been able to be turned like that if they weren't being forced to be there every day).
Tests - Standardized tests are horrible, but not really because of the conception. While there are several smaller problems with the idea (for example basing
everything on test results instead of a more wide profiling of a student or teacher), I'd honestly say that the biggest problems right now are the companies that are making the tests. We've got horrible problems with graders, test questions, stupid testing overall, and the fact that basically everyone who handles any of that is forced to sign documents swearing themselves to secrecy means that almost none of these huge problems ever see the light of day. There are big steps that can be done there to fix things.
Practical skills - Personally I learned the basics of cooking, budgeting, and a few other skills while in late middle school. I'm also for the setting up of government subsidized trade schools. Right now the vast majority are for-profit ones, which means that you get a basically worthless education while paying several times more than it would cost to go to a state college and take classes in what you are interested in.
I'd also say that there is a fair portion of skills learned in high school that
do have practical applications, they just aren't ones that people normally think about. For some easy ones things like algebra show up in everyday life fairly common. Simple things like dividing up a check or doing a rough calculation of tax is algebra. Geometry isn't that uncommon either, personally my family has built a fair portion of our own house, and geometry is dang important when you are doing things like building decks and laying pipes.
English doesn't seem like it's that important, unless you know a secret. There have been several institutes that specialize in nothing but testing, to help people figure out things about themselves (what careers might be a good fit, where might they be successful in life) and so on. When queried what the biggest factor they found in relating success to anything else, every one queried gave the answer of "vocabulary size". Having a large vocabulary and knowing how to use it to essentially sound smart and sophisticated was the biggest common factor any of them found with success in life, and that's what English is for. Things like physics, chemistry, or biology? Not so much, though I can say that I've used the basics of knowledge in all three to occasionally accomplish things that I wouldn't have been able to do without the knowledge. In history, on the other hand, probably the most important thing to learn is how people think. Names, dates, and places aren't the important things there, it's the why's that matter. If you can learn how people think, then those are lessons you can apply later to other parts of your life.
So in all I'd say keep compulsory education, but open up more routes for later in life when students actually can tell what they are doing. I've mentioned this several times before in other places, but the fact is that, physically, your brain isn't truly developed enough to know "what you are going to do with your life", until you hit your early 20's, because the parts that deal with deep self-introspection just haven't fully developed yet. Sure you might think you like art instead of math now, but by forcing you to keep all of your options open while you are younger and physically unable to truly know yourself we make it so that you don't accidentally lock yourself into a path only to discover several years later that you really never wanted to be an artist. (This is also the reason why the vast majority of college students switch majors at least once; they are finally developing enough that they can know what they actually want to do with their life.)
Also make music compulsory. My dad has a two-inch thick folder completely filled with studies about how being involved in music improves literally every aspect of your life, from your reading, writing, and math scores, to your friendships, to the amount of trouble they get into, to your personality, to your average success levels, everything. He has another folder with some 50 or so stories from students who have literally had their lives saved from suicide or whatever by being involved in a music program. Seriously, get people involved in some sort of music program, and everything else gets better just as a side effect.