I am going into a high school in Florida at the start of year 10, since I have to finish junior high school first (in my country that is grade 7-9). Will I be able to go straight into an AP class in my sophomore, or will I have to wait until junior year to do that? I think going to an AP class will not be outside of my capability, since the year 9 syllabus in my country already overlaps a lot with the year 10 or even year 11 contents in America.
Depends on the policies of the new HS.
Every US high school has different rules/requirements for AP classes - some have prerequisites or limitations on how many a student can take. Check with the specific high school.
Only your new high school can answer that.
In the US things vary from school to school so you need to talk to the school your attending. Classes do not go the same order at all schools. For instance some schools 9th graders thake ap human geography, some US History 1, some may allow APUSH, some start with word history etc. At my high school world history (any level - college prep, honors, or AP) is an 11th grade class whereas another school it might be a 9th grade class and APUSH not available before 11th grade. Science also varies a lot such as 9th grade requiring physical science (not even offered at my high school), physics, biology etc. Some schools allow students to take AP Chemistry without taking honors chemistry but my high school requires both honors biology and honors chemistry to take AP Chemistry or AP biology.
Math probably has the most standard progession such as algebra 1, geometry, algebra 2, precalculus etc but middle school math varies as well so kids start high school in different math classes. For instance many kids start in geometry at our high school but without taking a special summer class you pay for no one can start higher whereas a different middle school may cover algebra 1 and geometry etc.
Ask you school counselor about both policy and how it applies to your situation - there are often exceptions. Our school’s official policy is that AP classes start with a single course (World History) in 10th, to prepare students for the rigor of “college level” AP classes junior and senior year. But my D had one AP last year in 9th, 3 this upcoming year in 10th, and one of her friends was in AP BC Calc in 9th. We can hope schools are wide enough to offer sufficiently prepared students the ability to take appropriately challenging class when they are ready, not when they’ve hit some magic number.