First, make an introduction about school and emphasize importance of class attendance.
Figure out what factors you want to handle: traffic, sickness, you woke up late. etc.
Make an intelligent guess: These factors do not affect class attendance. or Traffic affects class attendance more than being sick.
Find out how you want to get the information. You can do a survey asking: what affects your class standing? Are you mostly late or absent? Why are you absent/late?
Show what you have using a table (Pie chart/ bar graph)
Then type what you found out: Like people are late because of traffic or People are more late than absent because of sickness. The biggest factor affecting attendance is ____ .
And that's it :)