I would reword it to say: If you didn't EARN the grade you wanted, its likely you didn't do the work you're capable of". My new favorite poster (which is FREE and ready-to-print from Teachers-Pay-Teachers)
Free set of printable CRITICAL THINKING SKILLS Posters! Great for any secondary classroom! They come in two sizes! These differences are so important to know, especially when differentiating between persuasive and informative writing.