I am in Year 8 in the UK which is grade 7 in America and you just need to do some revising,all your homework but don't be such a geek as people will make fun of you, i get pretty high grades and do all my work, yet teachers will appreciate extra work or homework plus if you have a strong relationship with your teachers they will get your grades higher and they think you are a good pupil :)
1. 6th grades exist so the probability is 1.
study for the next test and get an A+ on it which will raise your grade
You can take a cerent test or get good grades
It means your grades are good, that does NOT mean you are smart.
Depends on how your teacher grades. Generally, that is not a very good grade. But it depends on the "curve" as to where the cutoff is for each letter grade.
That depends actually. I think 6th grade should be a review of 5th grade. let me think about 7+ grades
1. 6th grades exist so the probability is 1.
Math is where you learn numbers and how to count, so 6th grade math is just harder! Its that simple.....
getting good grades
Grade 10. Grade 9 gets you prepared for Provincal Exams
The proper way to say it is 6th and 7th grade even thought it is two things not 1 u still do not use an s.
spelling words for sixth grades
study for the next test and get an A+ on it which will raise your grade
You can take a cerent test or get good grades
Of course A plus is a good grade its probably one of the best grades you can get!
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. 
force him to study and punish him if he gets bad grades.