oooh thank you so much ...by the way i'm cie not edexcel ....this is valid for cie also right?? ...and sorry but what's UMS? thanxxxxxxxxxxx
Well, there is no concrete explanation for how an A* is calculated on the CIE website and I've written them about it a few days back and am hoping for a reply soon. I'll PM you if I get it.
However, the most I can say is that your teachers are correct; the closest to the explanation on their site of how grades are determined by CIE shows that they consider a 50% of AS-Level results and 50% of A-Level. Given you have a B in Paper 2 implies your UMS (uniform mark scale, overall percentage scored with the highest mark scored in the entire session taken as 100) must be lower than 90%. Since A* means an overall percentage of 90 and above, so it'd be hard for you to balance it out in A2.
BUT, don't give up; you never know, if you work hard you could score an A* anyhow. Don't give up!