I had a pretty swell time in high school, but I do have some complaints. Some of these may no longer apply because I went to school a million years ago.
My first complaint is the lack of courses. If you wanted to learn "X" foreign language, or "Y" specific skill set, you were out of luck. Unless you went to a rich person high school that offered those things, (which depends on where you live, and that depends on your parents' income), you'd never have the opportunity to learn what you are actually interested in.
(My school only offered Spanish and German, while others offered Japanese, Arabic, French, etc. That same rich person school offered computer science courses and other introductory programming courses, while my school didn't own any computers. Again, I went to high school a LONG time ago)
2nd major gripe is that you are punished for experimenting with new things if you aren't immediately fantastic at it. Say you took Spanish for a year, and were okay at it, but you also want to see what German is about. You take the German course the next year, but then realize you suck at it. Depending on the school, you aren't allowed to switch courses and have to struggle through the entire quarter/trimester/semester and get a garbage grade. To add insult to injury, your school requires at least 3 years of a language, so now you take Spanish II the next year, except you forgot everything from Spanish I because you took German in between (Or you could take German II and fail harder).
3rd gripe is the permanency of everything and the inherent unfairness of income or body type. Oh you got a D in a foreign language course? Say goodbye to any school with a high GPA requirement or potential academic scholarships. Want to volunteer for something to build your resume? Oh, you have two working parents and need to stay home to watch your little sister when she comes back from elementary school. Want to try out for a sport so you can aim for a sports scholarship? Nah, you are just a frail, 80 lbs kid who will probably break at any physical contact. You'll never get off the bench even if they let you on the team. The school also doesn't have a chess team or anything intellectual, because those aren't popular and nobody is allowed to start anything because the school doesn't have the room, the staff, and/or can't afford it.
(My school only had a basketball team, a football team, and a very poorly funded/unpopular soccer team. Surprisingly there wasn't a baseball team. There was a band, but you had to buy your instrument, and I was not doing that. I was not interested in instruments, so it didn't matter)
Then we have the ever-raising education standards and the ever-raising cost of tuition. Want to see if being a welder or something is cool? Sorry, no Vocational-Technical school. What? You don't even know what a welder is? Your school made no mention of any trades? You think every job requires a college degree because your high school only teaches for college prep? I guess your only shot is to study hard and then go to college, otherwise you'll be stuck working at the factory with your dad making slightly more than minimum wage.
College brings about a new set of problems, but there are some cool things you can do (Academic Restart saved my future).
First and foremost issue is the cost. If you had crap grades and couldn't get any scholarships, you had to take out loans. Otherwise, you were basically forced to go to a community college (a great deal by the way) and try to get your basic stuff out of the way, assuming you even knew what you wanted to do at that point. You also had to make sure the 4-year school you wanted to go to in the future even accepted credits from the local community college.
Second issue with college was the caliber of students. If you came to terms with the fact that you aren't a talented person and are also poor, that meant that you had to take courses at a cheap public college/university with a large number of other poor and untalented individuals. This leads to a lot of wasted time in classrooms where people are asking questions because everything is beyond their understanding. You also run the risk of dealing with a lot of drug/illegal activity. The cheaper the place you go, the higher the crime rate. I've known people to have their books stolen because of how overpriced they were. There were also issues with rampant drug use in the dorms and loud, obnoxious alcoholics.
I could go on and on, but I feel like my wall of text is lengthy enough as it is.