Stevenson High School's most recent graduates matched campus records on the ACT college-entrance exam, school officials announced.
The students in the Lincolnshire school's Class of 2012, who took the test at various times during the 2011-12 term, posted a composite score of 26.2 out of a possible 36, officials said.
It was the third consecutive year students averaged 26.2 on the test, The Class of 2010 set the high mark, beating the previous high score of 25.7.
That score was reached in 2007-08 and matched in 2008-09.
The Class of 2012's composite score was far above the state average of 20.9 and the national average of 21.1, Stevenson officials said.
The ACT includes a multiple-choice section covering math, English, reading and science. An optional writing section measures skill in planning and essay composition.
According to the school, 1,038 graduating seniors at Stevenson took the ACT last school year. Juniors take the test as part of the Prairie State Achievement Examination, too.
The scores students receive the last time they take the test are the ones that count.
This past school year, Stevenson students set a new school-record on the English test with a 26.6 average. Students also tied a campus record with a 27 average on the math score.
Students tied the school record in science with a 25.3 average.
Finally, a 25.3 reading score was the second-highest in school history.
"What's really impressive about our ACT scores is the fact that we're able to remain at such a high level with more than 1,000 students taking the test every year," Stevenson Superintendent Eric Twadell said in an email. "That's a testimony to the great work our teachers do in the classroom every day."