The key reason that your junior year matters is this: The high school transcript you will ask your school to send to colleges is your academic record for the first three years of high school with your junior year record as the last one with your grades on it. You started building your junior record this fall. Review your report card and resolve to continue earning good grades or start earning better grades and doing better overall by the time the semester ends. You should be preparing for the SAT and/or the ACT so you can have scores to send to colleges when your college application process begins. Check on colleges of interest to you and see if they require SAT subject tests. Even if they don’t, you need to consider taking SAT subject tests just in case you find later that you need them for a particular school that you add to your list of colleges. Review and do practice tests on both the SAT and ACT if you are not sure which test is the right one for you. While knowing what each test requires may be helpful to you, nothing beats your experience taking practice tests to determine your test option.
Monitor your grades often. Your junior year academic record is the last record the admissions office sees when you start applying to colleges next fall. While your courses and grades have mattered up to this point, you need to ensure that your junior year grades trend upwards. Poor grades in junior year tell colleges that your work habits, among other things, are not consistent. If you are taking three or more Advanced Placement courses, you need to ensure that your grades in these courses are A or B. If you must drop a course for any reason, do so before your school’s stated last day to drop classes without penalty. Manage your academics and extracurricular activities well. Avoid misuse of time by avoiding multiple extracurricular activities. Focus, instead, on one or two that truly interest you.