Company Commander as a Junior?
Every JROTC system works a little differently. I was a Battalion Commander as a Junior and nobody thought it was odd.
USMA 1994 makes an excellent point. I know a boy who enlisted so that he could be recruited to USMA from the pool of soldiers rather than college students or students coming straight out of high school and his National Guard basic training starts at the same time as USMA CBT... a lady from Air Force told him he'd be better off withdrawaling his applications for the SAs altogether because his priority to the guard. He protested, stating that officer school trumps being enlisted and that acceptance to an SA would cancel his contract with the guard, but they still did not update his information. Needless to say, he's in some trouble now with figuring out what he should do. You don't want to put yourself in a scenario like this one.
Finish high school, stack up on STEM classes, and challenge yourself while leaving time for your extraccuriculars.
Take the standardized tests ASAP and take them WITH WRITING! The SAs REQUIRE writing scores! My RC told me a story about a girl who sent her 35 ACT score to USMA without writing and he told her to retake it with the essay...she did not, and consequently did not earn an offer to West Point.
If you have any medical problems such as an academic skills disorder or vision problem, get tested early. See your pshyciatrist, eye doctor, or whichever one you need to see and bring in the minumum standards that the Army requires to admit someone with your condition. Ask him/her what you need to do and do it. This is something you have to get a head start on, as DoDMERB can turn into a serious problem later on in the process if you're not prepared. As someone who had to go through the waiver process, I can tell you that you want your medical qualification early.
DON'T forget to apply for nominations! Your MOCs should have deadlines posted. Keep those deadlines somewhere!
PREPARE for the CFA. Start early! The earlier the start and the harder you work, the better you'll do! Consult experienced fitness coaches and ask if what you're doing will actually help. Don't waste your time.
Make sure you're in sports...from what it looks like up there, you don't appear to be in many. Join especially track or cross country (if you have time) and lift in your free time to make sure you're not losing push-ups and pull-ups. I can't tell you how important this is...
Apply for SLE when it opens. You need SAT/ACT (or PSAT, but don't rely on that...) for this! I strongly reccomend taking both tests and submitting them to USMA so they judge your profile based on an updated score. Please don't be discouraged if you are not selected for SLE. It is primarily your academic scores that determine whether you go or not, and 1. those can be improved 2. USMA Admissions will judge you for acceptance with the WCS. I was not selected for SLE but recieved an LOA to USMA. It happens.
Apply to Boys/Girls State! Plug into Google and search your program followed by your state. For example, Google "Boys State Wyoming" and it'll pop up. ALL 50 states have Boys/Girls state--Hawaii started theirs very recently. That being said, you have no excuse not to apply to Boys/Girls State! At Boys/Girls state, the positions of Governor/Lt. Governor or going to Boys/Girls Nation will net you even more leadership points! SLE does not give you points, so if they happen at the same time, prioritize State/Nation.