How can i make my 5 year old more attentive to studies?

my son has started kg1 and he is not doing well in cl.he is brilliant meaning he can speak english fluently(bengoli is our mother tongue.eng is second language)but he is reluctant to write or do homework. when ever i tell him to study he sharpens his pencilsor breaks his erasers or doses off or writes poorly intentionally. then after hours of patience i get angry and shout or scream. i hate to do this. he is a brilliant boy but he wouldnot study. in cl the 'silly' students are getting ahead of him .but he can download games, draw in the computer, cut and make cards, sclupter and also read some . but at school he just stares and doesnot talk. the teacher probably thinks that he is stupid. what will i do? shall i hire a private teacher ?