Transcript from an International School

I am an international student accepted into UCSD. They require my ninth grade school, which is in China, to send my transcript to them directly in a sealed envelope. I asked my school to do so, but got the response that they are not responsible for sending it. Now I’m stuck. I have the transcript in a sealed envelope now, but the school will not send it for me- what should I do? Shall I just send it myself?

Anyone? Needing serious help now

If the transcript is sealed, you can send it yourself or better, take it down personally.