RelativeEfficient493's journey

I'm currently in the job application process for a teaching position with CPS, and I've hit a bit of a snag regarding references. The hiring manager has specifically requested a reference from a principal, assistant principal, or someone from the HR department at the school district where I worked as a substitute teacher last year. Unfortunately, due to the nature of my role, I don't have any direct relationships with the administration since I was constantly moving between different campuses and primarily interacting with students. I spent the year as a substitute teacher across a large school district, which made it difficult to develop the kind of rapport needed for a reference from an administrator. I was also a full-time student, which limited my ability to take on long-term assignments that might have allowed me to build those relationships. The HR department has stated they can't provide a reference letter since they had minimal interaction with me after my initial hiring. However, I do have a teacher who I frequently substituted for, and she is willing to provide a reference. I'm considering asking the CPS hiring manager if this would be acceptable instead of the requested principal reference. I plan to accompany her reference with my job offer letter and any proof of employment they might need. I'm also providing supervisor references from my previous jobs, which the hiring manager requested. I'm just unsure how to approach the hiring manager about the teacher's reference and if there's anything specific I should avoid doing in this situation.