Help with high school grades and tests?

im a freshmen in high school and im asian.. i want to get all A's but i just can't get good grades on tests. right now i have all B's but 2 A's. If i just know how to get A's on tests i could get an A. everytime i try to study something i just cant remember it. can someone help me. im sometimes negative and think i cant do it. please help. the cl im getting b's are biology, geo, english and spanish2. math isnt that hard but i cant remmeber terms for bio and spanish. and i dont know hwo to write essays i always get 4's instead of 5's please help!!!!!!!!!!!