Help with XM Directory Design and Governance

Hello,
I am looking for some examples of how other K-12 organizations have designed and managed their XM Directories.
My organization is very new to Qualtrics. We are not quite a month into our license. I am the brand administrator and have been tasked with designing, managing, and governing the XM Directory.
My initial plan was to have a student directory and a legal guardian directory. For the legal guardian directory, I wanted to randomly select a student to represent the survey if the legal guardian had more than one student. It is not working out how I had envisioned.
Example:
I created a contact list based on my legal guardian directory for those whose students participated in a particular program. I was under the impression that the embedded data in the contact list wouldn't change when I updated the directory.
After deploying a survey to this contact list, I updated the directory. The embedded data for LGs with more than one student enrolled changed - specifically the student representing those LGs. The embedded data within the previously created contact list was also updated. This caused some of the students being piped into the program-specific survey to not actually be in the program.
I am now brainstorming new ways to design the directory that doesn't end with parents with 1+ students enrolled receiving a survey invitation for each student enrolled but also takes into account the relationship between directories and their associated contact lists.
How are your directories designed? How are you updating/managing contacts in your directories? How do you ensure others within your organization do not compromise the embedded data when they upload a contact list?
Any and all tips, tricks, and advice are welcome. 🙂