You want your children to do their best in school. So it's important to let them know the value you place on effort.
For instance, when your children show you a test score with a high grade, don’t just say “Great job!” Instead, say, "I know how hard you studied. I'm glad your hard work has paid off."
When they finish reading a book (or finish a project), you can say, "You made a real effort to finish that book (project). I'm proud of you."
Also be sure to recognize your child's efforts even when they may not have resulted in success.
Source: The Parent Institute