School isn't for me why?

i know how important it is to graduate high school. I also know how much my mom wants to see me graduate high school. But lately i just im sad about my life like its not that i dont like school its just that when im at home doing my thing playing world of warcraft, hanging out with the people i grew up with im happy and i get along with everybody but when im doing homework or going to school everythings just so bad. i get this feeling when i look at math or a story i have to read and its just like i get very angry and frustrated and i dont understand it much no matter what when i have math work i dont get it i read the book still dont get it i go online and look for tutorials or something that will help me understand the material better and i just dont excel! i dont get the work i dont have fun doing the work and even when i do the work right i dont feel any better about myself. i hate school like any 15 year old would. im homeschooled through opportunities for learning and i just i dont know whats going on i mean it wasnt ever like this until i actually got to highschool. now im being threatened of being removed from the program because it takes me long to do my work and well im really unhappy with my life so far. up until highschool it was never like this. apart from the goons that hang out in the street all day, i have no friends my only real friends are potheads and pretty much my cousin who still goes to regular school and i only see him everyother day he doesnt ditch me to go hang out in his school with his friends.. anyone have any advice? like whats wrong with me? why dont i like school? why dont i feel good about it when i do something right?