You have completed the import and you have students who are not who are not linked to the correct teacher
Why does this happen?
1. On the import file, you had 2 teachers with the same last name in the "Teacher" column and you only had last names, so the import had no way to know which "Smith" it was and therefore put all students in the class with the first "Smith" it found.
2. You have a teacher who teaches an AM class and a PM class and need to put the correct students into each class. To do this, make sure to create 2 teachers - "Smith-AM" and "Smith-PM" as the last names.
How to fix
1. Manually - You can go in and edit each family and click on the student and add the correct teacher which will move that student to the correct class.
2. Import - make sure that the teacher listed in the teacher column has a unique last name for each classroom and that every student has that name spelled correctly in their row on the spreadsheet. In the case of two teachers with the same last name, just include the first name or first initial on the family import teacher column.