How many fourth graders are in the us?

There's no single, readily available source that tracks the exact number of fourth graders in the US. Data on school enrollment is usually reported by grade level *bands* (e.g., elementary school, middle school, high school) rather than individual grades. To get an estimate, you would need to:

1. Find national enrollment statistics: The National Center for Education Statistics (NCES) is a good starting point. They publish data on school enrollment, but it might not be broken down to the precise fourth-grade level.

2. Estimate the proportion: Even with aggregate data, you could try to estimate the proportion of students in fourth grade within the overall elementary school population. Assuming a relatively even distribution across grades K-5, you could roughly divide the total elementary school enrollment by six. However, this is a very rough approximation.

3. Consider variations: The number would fluctuate slightly from year to year.

In short, you can't find a precise answer easily. Any number you find would be an estimate based on broader enrollment statistics.