It is recommended that your request be sent via email, which provides an automatic date and time stamp. Given the challenges in school staffing and outdated websites, I’d recommend sending your emailed request to a few different individuals to ensure that the request is received and forwarded to the designated person. This includes the school psychologist, school counselor, principal, and/or special education director.
Many families use form letters/emails found online or ask their medical provider to write a prescription (script) for an evaluation or IEP. These templates often are outdated or refer to regulations and timelines from other states. I’d recommend that you not use these form letters. In addition, the school is not obligated to follow the doctor’s orders. The most effective requests I received when working in the schools included a brief history of the concern(s) and the current impact. It was easy for me to understand the nature of the concern(s), to follow-up with the family, and to loop in other relevant school personnel, such as the speech and language pathologist or occupational therapist. The email does not need to be lengthy or overly detailed. You do not need to “argue your case.”
From Arizona Department of Education: If a parent requests an evaluation, the school must, "within a reasonable amount of time not to exceed 15 school days from the date it receives a parent's written request for an evaluation, either begin the evaluation by reviewing existing data, or provide prior written notice refusing to conduct the requested evaluation. The 60-day evaluation period shall commence upon the [school's] receipt of the parent's informed written consent" "and shall conclude with the date of the Multidisciplinary Evaluation Team (MET) determination of eligibility."