How much power does the student think is in the home phone magnet? Enough to attract 5 paperclips? More? Less? The answer to this question can form the hypothesis statement for the science project.
 
For more on magnet science, check out these articles:
 
Science Activity: Measuring Magnet Power
http://www.education.com/reference/article/science-measuring-magnet-power/
 
Magnets and Gravity
http://www.education.com/reference/article/Ref_Magnets_Gravity/
 
Experiment with Magnet Magic
http://www.education.com/activity/article/Magnet_Magic_middle/
  
Here are some articles related to science fair projects that you might also review:
  
What Makes a Good Science Fair Project?
http://www.education.com/reference/article/Ref_What_Makes_Science/
    
What is the Scientific Method?
http://www.education.com/reference/article/Ref_What_Scientific/
    
Tips for Parents
http://www.education.com/reference/article/Ref_Tips_Parents_2/
   
Enjoy!