I can never focus on my schoolwork?

I hate school so much. I can never focus on my work, and if someone distracts me, it takes me forever to finally get back to what I was doing. The teachers get exasperated and frustrated with me alot (I dont blame them) and often when Im doing homework I wont complete it on time just because I cant focus on it for more than about 10 minutes. I love art and music and those are the subjects Im best at. Quite honestly I would much rather draw or play my bass guitar but my parents take them away until I complete my homework. (supposed to be motivational or something). My parents think that Im just lazy but I honestly try really hard to focus and i just cant. I dont know why its so hard for me, but its frustrating and getting on my nerves. Please help me and sorry this is so long!