Behaviour at school ? ? ? ? ? ? ?

i am in secondary school now but am not very well behaved :( the thing is, i will try to be really good and it will go fine, untill someone or something annoys me and then i get really angry and distracted in lessons. Like one time some kid gave me a dig on the shoulder and i went mental like scribbling my book and lobbing stuff everywhere. I am usualy quite bad at school, ignoring teachers lobbing stuff but dont fight and dont have that much friends, but i want to stop acting like a d**** which is what i am! thanks guys!