Our hypothesis that Dettol was the most effective disinfectant, was proven to be false. Clorox was the most effective disinfectant, followed by Dettol, and then the dish-washing soap.
Try to repeat the science fair project using other cleaning detergents like antibacterial soap, Listerine or Bleach.
How effective are alternative household cleaners? - http://www.uwex.edu/news/2001/3/how-effective-are-alternative-household-cleaners