Tips to do better on standardized assessments and tests in general?

Hi guys.

Ever since I've been in school I've apparently performed low, academically speaking. I remember the first month of school, I guess I went too slow I had to be switched to a classroom that was suppose to be more of my pace. And I kind of have / had "okay" parents, but they would always compare me to my cousins and say things like "Look at your cousin, he gets better grades than you." And now as I look back through my old elementary report cards, I've realized that I actually had decent grades. They were in their A's and B's range. But I guess I never had any supportive parents?

But aside from that, I've always performed academically low on state standardized assessments. Especially math. I guess because ever since I started school, I never had anyone really tell me "You need to take school seriously" or "Make sure you pay attention class" aside from the fact that I would get judged by apparently "low grades" which kind of led me to not really caring for standardized assessments, or taking school as seriously as I should've.

Does anyone have any tips to help me do better on standardized assessments, I guess?

Thank you.