I have a senior in HS. What do you mean by "scholarships?" Do you mean financial aid based on need, merit/academic money from the college or university, sports or activity-based scholarships, or scholarships the students apply for from corporations, etc. (for example my son applied for the "Amazon Scholarship")? There are a variety of ways in which students get college money and the qualifications and criteria vary widely. And yes, a student can be in the top 10% of their graduating class and not get a "scholarship," depending on what you mean by that and depending on where they choose to go to college.
Most college money comes from the school itself, either need or merit-based. The first and best place to start is by looking at individual schools--are their awards of money need-based, merit-based or both? Private schools generally give more money than public schools, although the more selective schools (think Ivy League, etc.) usually don't give any academic money. They don't need to do that to attract quality applicants or students. Their giving is usually need-based.
The next best resource is your high school's counseling office. Your child's counselor should have information about legitimate scholarships. Many of the smaller scholarships not affiliated with an particular college or university are local.
I should know this, but I can't recall off hand. I think there is a federal website where you can plug in your family's financial information and it will spit out what your family is expected to pay for college based on need. It is quite startling. The amount families are "expected to pay" is not realistic for most families. We are in the midst of filling out the FAFSA and CSS (detailed forms required for any sort of financial aid requests) and it is burdensome and difficult to fill out the forms. The good news is that with proper research and some flexibility as to where a student is willing to go to college, most good students can get some sort of financial aid or merit money. I have a friend whose daughter is attending a big, respected university for $6,000/year, which includes tuition, room and board. They did their research and she is fortunate to be good enough in a sport to get some money for that.
The key is to get started early, look around and research. I prefer research by word of mouth from experienced educators, finance experts and/or other parents. It will be more reliable than just checking out websites or searching the internet.