To find the total number of students at McCord Middle School, we can use the information that 200 students represent 40% of the total student body.
Let \( x \) be the total number of students.
According to the problem, we can set up the equation based on the percentage:
\[ 0.40x = 200 \]
To find \( x \), divide both sides by 0.40:
\[ x = \frac{200}{0.40} = 500 \]
Therefore, the total number of students at McCord Middle School is:
\[ \boxed{500 \text{ students}} \]