This exception means there are two rows that have the same student ID number in your data file. This may be problematic if the rows do not contain identical data. If the rows do not have identical data for that student ID, the first row that contains the student will import and the second row will cause the exception. The data in the first row will display in the application. You can concatenate the rows together (see SIE FAQs).
If the rows are truly duplicates, removing duplicate rows upon file creation is the best option. Your IT team would need to facilitate this process.