I am curious on how to do good in school if they changed the grading system to like 3.0 and 4.0 averages?

ok so my school changed the grading rubric so they made it super hard to get good grades a 3.0 means you did everything correct and met expectations and the school says that converts to an A- and my parents want me to get above a 3.0 and i predict that grades are decent i mean i have a 3.45 in science because i always go for the level 4 stuff and do goos on tests and classwork but in other classes you don't have a noppurtuniy to get a level 4 aqnd all you can get is a level 3 and like in math class they NEVER offer level 4 so if i miss one homeowrk or get one question wrong on a test my average decreases to a 2.9 which is approching **sigh** the school says that students are suppose to get like 2.5's the first semester then get 3's the second it's all a change over time but my parents don't understand and will get mad at me my grades are like in the high to middle 2's which is good cause it's like a B and then writing they don't exept late work so my dad made me do the work but she won't put it in the grade book so how will my paremnts understand or how can i do better ANY IDEAS!!!I am curious on how to do good in school if they changed the grading system to like 3.0 and 4.0 averages?
just ask the schools when do they change the grading system and do good in school.