The source for students is a collection of "custom students", uploaded through the CSV file on the admin panel, and the data received from your IT team. Editing the student.csv file on the admin panel will only affect the custom students that were previously imported through the student.csv, not the information within the Student SFTP Import. To manually upload custom students, please review the article, Optional (Admins): Manual Upload for Students.
IT article: Optional Admins IT Integrations