Hard work affects everything you do. If you are willing to work harder, then you will get better results. Check out some of the other Learning Tips questions for more information.
Some people are very smart but very lazy. You could be smart, but if you aren't willing to put effort into your homework and studying, you won't do as well. Often it is the people with some smarts and a willingness to work at school that do better than those people with more smarts and a sense of laziness. So yes, someone's amount of hard work can really influence their grades.
http://www.wikihow.com/Get-Good-Grades-With-Effort
Work very hard.
work and study hard
You study really hard and work hard.
To improve your grades in two weeks you need to work hard and work smart.
No, you will just have to work hard to raise that GPA.
no
in higher grades there is more hard work
Your grades should not be afected by having a detention. However, if you use detention time wisely and do school work or study, your grades may improve.
Yes,5th graders can get good grades. All you have to do is work hard and study. Plus, if you remember stuff for tests, hopefully you'll get a good grade. 
there is no difference just grades and hard work
wel that depends on how hard you work and how high your grades are
You can avoid it by studying and listening to the teacher. You should also work hard.