The educational requirements to become a hairdresser and beautician vary by location. There isn't a single set of grades needed. Instead, you generally need to complete a specific program at a licensed cosmetology school or apprenticeship. These programs often have entrance requirements, but they usually don't specify a minimum GPA from high school. Instead, they might require a high school diploma or GED.
In short: You don't need specific *grades* in high school, but you do need to finish high school (or equivalent) and then complete a state-licensed cosmetology program or apprenticeship. Contact your local licensing board or cosmetology schools for the precise requirements in your area.