NSCAS overview
https://www.education.ne.gov/assessment/nscas-system/#1669821216124-5042f972-ceff
ADVISER Resources
https://www.education.ne.gov/dataservices/adviser-resources/#1533221816265-b51e789f-abfc
ADVISER Data Guidance
Student ID's are found in the NDE Portal under a collection called ADVISER Person ID. There are specific persons in the district with access usually the Superintendent.
If you have questions about whether an ID is valid or which one should be kept, your district can open the portal and go to the ADVISER Person ID collection. All valid IDs are listed within.