Student <- Attendence -> Class
Many students, many classes, attendence is unique and is linked to Student and Class.
Class can show all attendences, Student can show all Classes.
A third table is almost needed in many databases dealing with two tables.
The White Paper for FMP Novices would be recommended reading.
The fifth link here http://forums.filemaker.com/posts/f6ed4be796?commentId=222931#222931
To put that in other words, if you have data in two tables and the relationship is "one to many", you have one one record in Table A that links to many records in Table B, the trick is to set up your report based on Table B. You can then use the relationship linking the two tables to place fields from Table A on your Table B layout in the Header, footer, grand summary parts, etc with Table B records shown in List View in the Body layout part.