We have had a parent exit survey form for many years asking reason for leaving, school communication, pastoral support, teaching and learning support, general comments etc.. It is currently a written form response. I am in the process of moving to a qualtrics survey the link will be embedded in formal email which includes the leaving documentation to the family. This way I will have the data at my finger tips for data analytics current and future.
I hope this has been useful information.
If you would like anything further please let me know, I am happy to share.