In many cases, hard work is necessary. This isn't always the case. For some, academic achievement comes easily. There will always be a few people that seem to accell without having to work hard. They simply understand and retain the information without having to put in the hard work that others must. Of course for most of us, hard work is necessary to succeed academically. Most of us will find some area that we are weak in and therefore have to work extremely hard to achieve excellence in that area.
I am wondering if your point is that only students who work hard can achieve high scores or if your point is about policies that don't allow a perfect score. The above posters have dealt with the first possibility in depth so I'm going to address the second.
I do know of teachers who have policies against A's or 100 %, it being that nothing is perfect. However I disagree with these policies because I don't think giving 100% is necessarily saying that an assignment is perfect. I think if we are working on a 100 point scale then the best work that does all of the things asked of the student, and does them well, even if it is not perfect, deserves a 100. I know this policy is particulary popular in terms of not giving high grades early in the school year, under the assumption that those grades can only be earned over time. I also disagree with this as what you are assessing at any given moment changes. I don't expect a student in the first month of school to be doing the same quality work as one in the last month of the school year. I am grading based on the assignment and the expectation at that time and place. I'm not going to say you can't get an A, I am going to say that A level work gets harder over the course of the year and over the course of each consecutive school year.
There are some individuals who, regardless of how hard they work or how innately brilliant they might be, simply have difficulty performing well in a testing situation. They may not be able to organize the information in their heads so they can easily recall it when under pressure; they may over-analyze questions and give incorrect answers due to being misled when they consider complications that aren't really there; they may face other challenges in the exam setting.
The point is that the generalization presented to start this discussion is just that - a very broad generalization. There are many examples of ways in which it can be disproved.
I agree with above posts and would also add a comment about the "99%" part of your post. That kind of score is near perfection and perfection is rarely achievable, and while striving for excellence is to be commended, striving for perfection is a potential waste of mental and emotional energy.
There are people who have photographic memories, and those who have great ability to memorize; both these groups do well on exams. Later on, however, they may seem less than brillant since all they have done is regurgitate information. On the other hand, a student capable of independent thought and analysis and synthesis will later seem more "brillant" after tests are all put away.
I, too, must agree with post #2. For some students, certain subjects (even all subjects) do not require the work others may have to put into it for high grades. Albeit a long time ago, I do not remember studying very hard and doing very well in my high school classes. That being said, college was very different. I would study my very hard and still have some issues.
Many things play into grades besides studying: mastery of subject, good testing skills, a good night's sleep.
I agree much more with Post #2 than with Post #3. There are plenty of people for whom most tests are really not that hard. They are just naturally smart enough to absorb the information and are confident enough to take the tests without fear. They can get very high scores without having constantly having to study.
The hard work part is definitely correct. I don't know if you necessarily need to be "brilliant" or not. I guess that might depend on the exam; some are a lot more difficult than others.
Studying day and night might be a bit too much for some folks. It's possible to burn out and begin to lose effectiveness with overwork. Consistency is definitely a plus, however. How about studying on a regular basis, even daily, but not necessarily "day and night."
I do not agree with this statement. Some students find it easy to achieve very high scores on exams with very little effort. Some others have to put in hours of hard work, as you describe. I have taught both types, and the trick is to try to design assessments that reach and challenge both sets of students.