You just need to convince them that transcript is nothing but a statement of marks or grades which is signed and sealed by the school official with the official seal. Remember that transcript just like the recommendation letters must be sealed in an envelope preferably one with university logo.
Sometimes it may take a while so it's better to contact your school well before in time such that you get it on time. An application is not considered to be complete until your official transcripts are received by the department you are applying to. So the US students are also advised to apply for their transcripts as early as possible once they are finished with the required tests.
One more piece of advice to international students relates to picking the service provider to send the admission documents. Choose one which is reliable even though it's a little costly as otherwise you may have to feel lots of stress when you see that your documents are not delivered on time by a cheaper courier service. So in the long rum you are worse off.
P.S.- I see from the stat that many students are probably visiting the blog but they refrain from making comments and so I am not sure which information I should stress on. As I can't remember exactly the questions I had when I was applying, I would encourage you to post your questions and comments and I will try to answer them as perfectly as possible. This I also feel that my time is used in a productive way. Thanks.