Many High School juniors sat for multiple college entrance exams this term. Now that summer is upon us it would be wise to find out which test results are better. Check out this conversion table here If your scores on one of the exams (ACT or SAT) are markedly better, then you should focus only on the test with the better results.
Dedicate your summer months to improve upon the exam which you did the best as a junior. When you get back into the swing of things in September of your senior year, plan to sit for either the September ACT or the October SAT. This should be your final best effort. Then you can focus on your college applications.