I have a lot of imaginary worlds, but I’ll just answer the questions based on one of them XD
The education system for ordinaries—humans without special abilities—is very similar to what we have on Earth. Six years of elementary school, followed by three years of junior high school, and then three years of senior high school.
Children typically start school once they’re six years old, but some children may start at five-and-a-half or five. After that you can pursue a bachelor’s, a master’s, and maybe a PhD if you want to go that far.
Those from the villages or poor families usually just go to vocational or technical schools after graduating high school, or they may only pursue education up to high school. Those from more urban areas are more education-oriented.
As for gifteds—humans with special abilities—they’re all sent to academies, which are schools established specifically for educating gifteds. Gifteds start schooling once they reach the age of seven, and they typically graduate once they’re nineteen or twenty.
They share some similarities with ordinary schools: the way they’re split up (six years of primary school, three years of junior high, three years of senior high) and the subjects taught (e.g. language arts, arithmetic, the sciences). However, academies are typically boarding schools with vast campuses and state-of-the-art facilities, whereas ordinary schools usually aren’t (although some ordinary boarding schools exist). Academies are also known to be stricter and have a more rigorous curriculum. Academies used to have two pathways: the path of the guardian (basically you use your powers to actively defend settlements from wild beasts), and the path of the neutral (prepares you for life as a “normal” person). However, in recent years, there has been such a huge shortage of guardians that basically every gifted child is forced to take the pathway of the guardian.
The only similarity I can see is that they’re split like this: six years primary school, three years of junior high, and three years of senior high. I don’t really know anything else because I didn’t go to a local school—I went to a private international school that uses a different curriculum from local schools 
They’re typically paid well. Teachers at academies and private schools make the most money. Those teaching in villages and small towns don’t really get paid well, but they’re not severely underpaid—maybe just slightly underpaid, if they’re even underpaid in the first place. They earn normal salaries.
It really depends on whether you’re a gifted or ordinary and which village/town/city/city-state you’re from. For ordinaries, rich people can afford to go to whatever private schools they want, although some go to government-run schools. Everyone else studies at government-run schools, which are all free. Non-rich people also tend to study at schools that are in their zone (the area they live in), and they can only go to school in another zone if they’re pursuing a subject available only at that school, if they’ve received a scholarship from that school, or they’re paying for a private education.
As for gifteds, all of them go to good schools and experience the same things, regardless of their background. They typically attend academies that are nearest where they live, and that’s where they’re usually assigned to study. However, if you’re very wealthy—as most gifted families are—you can afford to send your gifted children to a more “prestigious” academy, usually the one that’s affiliated with a rich city like Ildor. Even then, most rich parents don’t feel the need to pay extra to send their gifted children to a more prestigious academy, since all academies are prestigious in the first place, even the “least prestigious” ones.
My main character never went to school.
Uh, huge spoiler alert. Basically he’s the son of an evil sorcerer, and he was never sent to the academies to be taught. When his evil parents died, his mother’s family took him in. They didn’t send him to the academies either because he looks exactly like his evil dad, so out of protection, they homeschooled him instead.
When he was a young adult, something happened and he lost his memories and almost died in the middle of nowhere. The deuteragonist, a female guardian and academy graduate, found him and took him under her wing. There, he received a second education. She would mainly mentor him in terms of helping him wield his special abilities. As for the “normal” subjects like arithmetic and social studies, she would just assign textbooks to him and he’d read them.
Guns aren’t a popular choice of weapon. Most citizens are taught swordsmanship or combat in some form. Guns came with Humans, so Humans are the ones that use it the most. But policecitizens learn everything. Just in case.
