To motivate student employees, Stuart Carey, owner of a Sonic Drive-In Restaurant franchise in Tucson, developed a simple bonus plan based on their grade-point averages. If a student works at Carey's fast-food restaurant for a whole semester and earns a 2.5 to 3.0 GPA, Carey awards a 15¢-per-hour bonus for hours worked that semester. He ups the ante to 25¢ per hour for students earning better than a 3.0 average.

The cost has been marginal: Carey spent $1,200 for the most recent semester, less than 5% of payroll costs for that time period. Each of the 18 employees who were eligible for the GPA bonus got one. "The hardest part is, they are the best students, so they get better opportunities and move on," says Carey.

But he's had no problem attracting replacements. The system so impresses a Tucson high school's counselors that they recommend students apply for jobs at Sonic Drive-In.