The Highest Awards that a Girl Scout can earn are the

Bronze Award -
Junior Girl Scouts 4th-5th grade

Silver Award
Cadette Girl Scouts 6th - 8th grade

Gold Award
Senior (9th -10th) or Ambassador Girl Scouts (11th -12th)

For more info on each award look at the individual pages.  The pages include info about the process for Girl Scouts of Orange County as well as links to GSUSA resources.
For information and a comparison of the requirements for Take Action Projects from journeys all the way up to Gold click here