To find the total number of students at McCord Middle School, we know that 200 students represent 40 percent of the total student body. We can set up the equation as follows:
Let \( x \) be the total number of students.
According to the problem: \[ 0.40 \times x = 200 \]
Now, we can solve for \( x \): \[ x = \frac{200}{0.40} \]
Calculating: \[ x = \frac{200}{0.4} = 500 \]
Therefore, the total number of students attending McCord Middle School is \( \boxed{500} \).