Cover letter for a School Counselor?

Proper structure of my cover letter

I'm from Vietnam and in my country we don't really have school counselors, so students usually ask for help from their Homeroom teachers. I'm asking my counselor to send my score reports to some colleges via email attachment, and they require that the counselor "clearly indicate that the email is sent by a school official, not a student in the cover letter". I searched "cover letter" on google and I've only found letters that come with resumes and such. Does the cover letter in my case mean the signature at the end of every email, which includes name, occupation, and contact information? Or is it a short letter explaining that she's a school official?

It would be great if you guys can provide a full example of this kind of cover letter.
Thank you so much!

Khoa, this means that the university is asking your counselor / Homeroom Teacher to write the cover letter on a piece of typewriting paper that has the school logo on it. The school stationery with the name of the school, address, phone number, website, and other pertinent information printed on it would be best. On the part of your teacher, when the signature is placed at the end of the letter, the teacher must indicate contact information such as his work email, work contact number, and position at the school.

This is just a simple cover letter that could state anything as simple as:

This letter is being issued to support the documents requested by Khoa for his application to such and such university. The documents and this letter may be used by Khoa for any purpose that suits his need. As his home room teacher, I have authorized the release of these documents and attest to its validity as having come from our educational institution. You may contact me for further details in the event of any questions arising from the documents attached. Thank you.

Then the information and signature of your teacher follows. Now, the aforementioned example of a cover letter content only works if you are not being required to attach a letter of recommendation as a cover letter as some institutions are prone to do. Make sure it just a cover letter that you need because the recommendation letter contains highly different information. For the format of the letter, you can look up any example on the web. The format is the same for job and school cover letters, only the content changes.