The scale needs to make sense in US terms, which is different from Nigerian terms. The weight or meaning of the words changes even if the words are the same.
For instance, “very good” in France means you got Academic Honours that fewer than 10% achieve in the entire country. But in the US it means you’re not excellent, not outstanding, not among the top few in your year and not among the top few the teacher has encountered in their career. Same words… But not the same meaning at all!
If your grading scale has them, F9= US F, D8= US D, D7= US C, C6= US C+, etc.
In other words, a C4 is not a US C. (A US C is… not good.)
Colleges will see you have a lot of A1-B3, which is what they want to see.
Btw colleges will need to see your official certificate results both from junior school (Basic Education?) and the Senior School certificate (WASSC?). A photocopy that is stamped by an official at the school as being a true and verified copy and/or uploaded with your transcript is sufficient. (DO NOT send the one official copy sent to you.)
So, there were 130 in the STEM stream (ie., science group, or, in US parlance when a group of students are together for a common curriculum within a larger school, a " STEM academy"), 200 in Arts, and 100 in Commerce? Is that in 10th or 12th grade?
Work study is the right to work a certain number of hours every week on campus so you can handle your miscellaneous purchases yourself (toothpaste, new socks, a pizza…) typically it means you need to find a job somewhere on campus and the department or service (cafeteria, library, housing …) knows the college pays you every other week for the number of hours you have effectively worked. Most internationals get $2,500-3,500 per year, which equals about 8-10 hours a week, paid minimum wage. All colleges that provide financial aid will expect you to work.