Grades matter. Students think of grades that matter as the grades they will earn in their junior and senior year. But in reality all grades matter starting with some courses that count as college entrance requirements (foreign language for example) in the 8th grade.
I love to talk to 8th graders about what they will need to get into colleges they think are awesome. Explaining that their 8th grade class achievement will affect their chances to get into colleges they would like to consider has a powerful effect.
To an 8th grade student, 10th grade seems far, far away. Not only is it not far away but how hard they study in 8th grade (and before) affects how well they will do in all of their classes when they reach high school. Helping elementary and middle school students understand that academic achievement in each grade of school goes together like Lego's is a great example. Learning to read, comprehend, calculate, analyze, write, report and interpret in elementary school sets the stage for what students can do in middle and high school which determines where they can attend college.