Why haven't I gotten 'Graduate' achievment in Halo 3?

[Rizuk X]

I already have a little over 30 xp (2nd day of xbox live) but i haven't gotten the graduate achievment, why is this? I searched this question already but I'm checking if i'll get different answers than others... thanks

(my gamertag is same as my nickname here) Rizuk X
ok, thx. im a sergeant lvl 2 or sumthin so ill just keep playing, is it true that the higher your look sencitivity is the faster you lvl up or more xp you get?

 

[kyle]

I think you have to be a Lieteniut to Graduate.

 

[joevsyou]

umm what do you have to do for it? maby get your lvl higher

 

[B_U_L_L_Y]

i think u have to get ur rank higher