To find the total number of students in the school, you can set up a proportion based on the information given.
Let's denote the total number of students in the school as "x" and the number of sixth graders as 42. Since 30% of the students are in sixth grade, we can write the proportion:
\[ \frac{42}{x} = \frac{30}{100} \]
Solving for x:
\[ 42 \times 100 = 30x \]
\[ 4200 = 30x \]
\[ x = \frac{4200}{30} \]
\[ x = 140 \]
Therefore, there are 140 students in the school.
