Different schools have different requirements for admissions, including the minimum grade point average, or GPA, of applicants. For admittance to the University of Arizona, applicants need to have a overall GPA of 2.0 in each subject area, at a minimum. You are assured admission to the UA if your GPA places you in the top 25 percent of your graduating class.
How do you find if you're in the top 25%? Ask your high school counselor!
If your goal is to get a scholarship (or two or three!) to help pay for college to be competitive you generally need a GPA of 3.5 or higher. But there are plenty of other, smaller scholarships you might qualify for with a lower GPA.