By british airways from Hyderabad(India) upto london 3baggage from there 2baggage for students

I am going to USA on student Visa I purchased Air ticket starting by British airways from Hyderabad to london checked baggage allowance is 3nosx23kgs from london to Dullas I have to take American airways flight .as per ticket 2nosx23kgs baggage allowed.Being a student whether i will be allowed to take extra luggage in American air ways or I have to pay Extra money