Im a 19 year old freshmen.....?

im a 19 year old freshmen i just went back to high school i started insight schools of washington state i turn 19 on december 25 this year so that leaves me with only 2 years to graduate i heard that there was a test that i had to take and p inorder to graduate i heard that if i dont p the test i wont graduate im a very slow learner im taking 6 courses this year and im gonna do summer school this summer and next summer and also next year i will do 7 courses more if possible im trying my best to learn all that i need to take the test is this true is there realy a test that i need to take and p or i wont graduate if i take all these cles and p them i have realy good grades nth under a C im gonna work even during the holidays is there anything i can do to increase my chances of graduating what if i did all this hard work and p all my classes but fail the big test is it possible i wont graduate? did anyone have to take the test and pass it to graduate or did you guys just graduate?