There is a "chain of command" in school districts similar to private corporate business. in my opinion, one of the objectives in using certified mail is to insure it gets to the party that is ultimately responsible for making sure special education law is followed.
The US Department of Education oversees State Education Agencies (SEA).
SEAs charge school district Superintendents with primary responsibility of Special Education law.
Superintendents of the Districts typically designate a District level Special Education Director.
Each school campus has a person designated for overseeing campus level activities. Sometimes it's the principal and sometimes it's a separate campus department that reports to the principal.
You want the certified mailing to go to the designated district Special Education Director (not the campus level sp ed director).
I would likely address the letter to the campus Special Education Director and the Principal as a matter of protocol and courtesy; and cc it to the District Sp Ed Director. But again, the certified mailing would go to the District Special Education Director.
The school of hard knocks has taught me it is prudent that the truly responsible party to be put "on notice" so to speak. This action also circumvents the often used excuse of "we (upper administration) didn't know."
(And when that doesn't work, I start sending the certified mailing to the Superintendent -- but I don't think you are there yet.)
It's good to hear that you have the psychiatrist's letter. Be sure it gets to the District Special Education Department via attachment to your cover letter and, as always, via certified mail. Paper trails, paper trails....
Ex:
Date
Name
Address
Re: difficult child's name
School name
IDEA evaluation
Dear Mr/Mrs Sp Ed Director:
In response to Ms. Abc's notification, attached herewith is a letter from difficult child's doctor, Dr. XYZ, dated March XX, 2007 pertinent to the special education evaluation requested via my letter dated March XX, 2007.
Sincerely,
Mom
Attachment
You're doing good. Hang in there.
When you get this step done, remind me to introduce you to IEEs in the event you need that info in the next month or so.