Grade school is years long, so a skill you're supposed to know in 3rd grade is one that you need to be able to faithfully execute for the next 3 years. The fact

Grade school is years long, so a skill you're supposed to know in 3rd grade is one that you need to be able to faithfully execute for the next 3 years. The fact that you'll get a calculator in middle school doesn't help you if you're struggling through 4th and 5th grade.