Problem Solving Practice
If you want some simple practice, try CodingBat to get started! Language options include Java and Python.
Khan Academy has some great courses taught by professors dealing with computer science. Courses include Javascript, algorithms, and animation. Check them out!
USACO is the most prestigious computer science competition in the entire nation. For advanced prep, please check out their training website.
HackerRank has programming challenges and events that are taken globally. Make an account and join!
CodeHS has a bunch of coding courses dedicated to high school students, including one on prep for AP Computer Science A!
JUST FOR A HEADS UP, THESE WEBSITES ARE ALL BEST VIEWED ON A COMPUTER
For some beginner problems, check out HackerRank or CodingBat
Khan Academy has some great courses dealing with computer science. I suggest you check them out!
USACO is one of the most prestigious computing competitions in the nation. To prep for the advanced material, go to train.usaco.org!