its quite simple actaully
when he is with his freinds he can't be soft and polite with you because he's freinds
will laugh at him. Well... he's real freinds wouldn't make him feel bad or make fun of
him cause of that, but even so HE F E A R S that they will. Fear is the main emotion
making him do that.
Its basically same as he might be shy to kiss his Girlfriend near he's family and friends cause
he fears what they will think about it. But if he has done it even ONCE infront he's freinds he
will lose the fear and be confident about it.
Another reason might be that he trys to be cool for his friends, trying to show them that your
the love sick one chaseing after him. I mean... every guy wants a girl to chase after him and if he's freinds get that inpression he will look cool infront them and gain RESPECT from them.
there are SO many diffrent reasons for why he really might do that... I do not know the DETAILS of how he acts alone with you and how he acts with he's freinds , what he says and does. If I knew that I could probably give you the most accurate answer.
but in most cases... its all about looking cool infront of he's friends while he thinks that there is no way you might get offended by that.
But as I said real reasons depend on DETAILS... and AGE. As I see its Under 18... so that means age matters A LOT
if you want more detailed answer you can send me a message ^^