The letter grades reflect the value of the movie for its intended audience.  They reflect age-appropriateness but are primarily determined by the film’s overall quality and how well it fulfills its own aspirations.  A silly comedy, an adult thriller, and a thoughtful drama may all get B’s.  That does not mean all are of equal value.  It just means all deliver what their audience is looking for.  Age recommendations are just a guideline.  Every child is different, every family is different, and every situation is different.  A general rule of thumb is that material that is racier or more violent than you would see on prime-time network television is recommended for high school and up.  To determine whether a movie is right for your family, read the “parents should know” section of the review, which lists material parents might be concerned about, including sex, violence, language, substance abuse, and diversity issues, but also plot elements like loss, family stress, positive portrayal of poor judgment or behavior, and other factors that might make a movie inappropriate or a poor choice for some audiences.