Though we don't have a report for exclusively that information, we do have a report that includes it. The report is titled "Student Body Diversity" and it can be accessed by performing the following steps:
  1. Start from any product dashboard (Core, onRecord, etc.)
  2. Click Analyze > Reports
  3. From the Category drop down, select User Management -- Student Reports
  4. Click Run next to the Student Body Diversity report
  5. From the Run By drop down, select Grade
  6. Click Generate Report
The report that is generated breaks down grade levels by diversity (ethnicity), however, at the bottom is a total number of students per grade level. This report can then be exported to an Excel spreadsheet, where the unnecessary information can be deleted and you will be left with just the total numbers.