You're going to become a project for me.
In the US, you have resources like Khan Academy, you have chat channels, you have endless resources available to find assistance with your academic needs without resorting to paying anyone. I haven't heard of any school systems in relatively populated areas that don't have free and generally good quality assistance programs to help kids who ask for it.
Talking with school teachers in the US, there seems to be a fundamental difference between Europe and the US. In Europe, if a child does poorly in school, it's the burden of the parent to ensure that the student does better. In the US, if a teacher gives a bad grade to a student, the teacher knows that the parents of the child will be sending mails, making calls, etc... to argue with the teacher regarding the grade.
This is a shortcoming in the US system which says that if you don't get perfect grades throughout your entire primary and secondary schooling, you should expect to ask "Would you like fries with that?" for most of your professional career. This is because you will not have access to good financial assistance via grants, loans and scholarships if you don't have a totally flawless childhood.
Here in Norway, kids don't even get grades until they start in middle school and then, the first two years of getting grades doesn't really count other than placement in later grades. If you spend most of high school drunk and delinquent, when you're done, you can do a year in the military or two years in civil service, get assistance from the government with college prep and then move onto other careers.
It is actually far more difficult to get into programs for trades following a misspent youth here than to get into the university. A few tests is all it takes to get into the university here. If you pass those with sufficient grades, they'll give more or less anyone a shot. Trades however tend to start education in the 10th or 11th grade and if you miss your chance when you're that age, getting into a program that can assist with an apprenticeship can be difficult.
As for universities in the US, anyone with enough money that can pass an entry exam can go to a junior college. Of course, most of Europe (so far as I am aware) don't have junior colleges. It's university or bust. And while you're not likely to be admitted to study to become a doctor after a certain age, most other options are in fact available to you.
This is simply because the government (at least in Norway) will do pretty much absolutely anything to help you into higher tax brackets.