My grandparents can be quite mean to me...please help!?

Hi, my grandparents on my dads side have never been the nicest or most loving people. My dad's mom puts me down a lot, she yells at me sometimes and acts like I am stupid, when I am not. Her husband (my father's step dad) is even worse. He does everything my grandma does except he keeps on...for example he always asks me how I am doing in school and with my honors cles, I say really well and that I am on honor roll. He always says "Well MY grandson is so smart he went to John Hopkins and MY granddaughter went to Harvard...you are not as smart as they are". The thing that really puts me over the edge is when he tells me I am stupid for taking French because I should be taking Spanish. I find that I can learn Spanish whenever because I am surrounded by it and I prefer to learn other languages but to him he says "there is no point but if you were smart you'd know that." I hate how mean and degrading they are...and I have to visit them for about 4 hours. What do I do? My parents are divorced so my mom can't do anything and my dad tells me just to ignore my step grandpa and to never be disrespectful towards my grandma and how dare I say this etc. I am not disrespectful in fact I have taken their rude nature for so long I cannot take it anymore. What should I do? (P.S. The examples I gave are only a couple of a lifetime of insults) Thank you.