What Do I Do If Ppl Push Me Around?

im 13, in grade 8 and i just came 2 a new skool. The problem is that ppl (especially boys!) push me around. Kay, i usually wudd kick dere azz but, im kinda shy since im new. So what shudd i do? Oh yea and my mum said its kay if i beat them up(lol), but i dunno how 2 beat up a guy!!!