To find out how many students brought their lunch to school on Thursday, you can calculate 25% of the total number of students at Ridgewood Junior High School.
First, convert 25% to a decimal:
\[ 25% = 0.25 \]
Next, multiply this decimal by the total number of students:
\[ 0.25 \times 500 = 125 \]
Therefore, 125 students brought their lunch to school on Thursday.