I have observed over may years of experience that attendance greatly affects students' performance in mathematics.  I can only recall one student who was denied credit in one of my math classes that had a passing average and more than 28 absences (the old limit).  Sadly, I can point to many cases of students with poor attendance that failed. 

It is the nature of mathematics that its content builds upon itself.  Students must master each section before beginning the next section.  Consequently, it is imperative that students keep up, especially when they are absent from class. This is very difficult for students.  Although there are many resources available such as: text books,  e-books, posted class notes, podcasts and the many links on this site to name just a few, it is difficult to learn mathematics without the daily give and take that occurs in the classroom.  The classroom experience can not be recreated.  This is one of the things that make the study of mathematics so challenging.  It requires a sustained effort to make progress.  Absence from class interrupts the learning process and should be avoided whenever possible!

Euclid is said to have replied toKing Ptolemy's request for an easier way of learning mathematics that "there is no royal road to geometry"[2]. Charles S. Peirce, in his How to Make Our Ideas Clear (1878), says, "There is no royal road to logic, and really valuable ideas can only be had at the price of close attention."  (Wikipedia)

Mathematics is a powerful tool for understanding the world around us.  Its unique beauty can only be appreciated by those who have made the effort to learn its secrets.  It’s worth the effort!  See you in class!