You are still in junior high school and are able to enroll in a trade school? You usually need to be a high school graduate or obtain a
GED to go to such schools.
Or are you same age as average junior high school kids but somehow are beyond junior high school with your education level?
Or are you just planning your post high school studies a few years earlier then many often do?
If you are still in junior high school I suggest you pay attention in physics, chemistry, and math classes, now and through high school. Even the stuff that may not seem directly electrical related may come back to you when you get to studying deeper into electrical theory, or at very least will come in handy in other areas that are related to this field. You may find yourself a little into mechanical, hydraulics, pneumatic s on top of electrical in some instances in this trade, as well as general construction topics can come up and those can fall back onto some of the same sciences and mathematics abilities needed to understand them as well.
This is all just to make you better at understanding the technical side of things. English, social sciences, physical education, business, arts, are all things that may not seem important now, but someday you will see that at least studying them to the extent typically offered at the high school level is not a bad thing and that you do use some of that knowledge throughout your lifetime regardless of what career path you take.
Otherwise as far as studying the electrical field - start with finding just about any basic electricity concepts instruction book - they are what colleges/trade schools would use as a textbook for Basic electricity 101 type of a class, and read it. You really need to study this kind of material before getting too deep into codes or installation methods.