Why were some rows of my file not imported?

Before importing, See details lists each skipped row, with its number and reason:

• already at the school or higher in the file: same first and last name (accents and capitals ignored) as an existing student or an earlier row. If they really are two people, add the second one by hand and tell them apart (for example with a middle name).
• missing first or last name, invalid email, text too long: fix the row in the file and import again; students already imported will then be recognized as duplicates.

Completely empty rows are ignored without being reported.