The lesson for the day was about rhythm, but first-grade teacher Mindy Nguyen wasn't using music alone to impart the concept.
Nguyen read a poem and showed a painting depicting life in a city, then fired probing questions at the 21 youngsters sitting on the floor around her.
Can you hear how the city sounds? What feeling does it give you? What does the color red in the painting tell you about the city?
If they didn't quite get the connections she was trying to make about rhythm, they were learning a slew of new vocabulary words and an important educational lesson: Art is more than just pretty pictures.
In fact, at Chester Charter School for the Arts, it's the foundation of the entire curriculum and, school officials believe, one of the reasons it outshines every other school in the low-performing Chester Upland School District.
In the broad canvas of Chester schools, CCSA, with its 420 students, stands out like a Van Gogh sunflower. This year, it had the highest School Performance Profile - the state measurement of achievement - in the district and the third-biggest increase, from 46.7 to 71.7, in the Philadelphia region.
No other Chester school, traditional or charter, cracked 70, a number that the state considers adequate.
School officials also credit an intensive reading-intervention program for the success of the K-8 school, which plans to add high school one grade at a time, starting in 2015.
"Reading is a huge push here," said principal Akosua Watts, a former investment banker, who worked for Chester Upland for 10 years before joining CCSA.
Every teacher doubles as a literacy instructor, and students get five-day-a-week small-group reading classes. The results can be seen in Pennsylvania System of School Assessment (PSSA) scores. When the school opened three years ago, 36 percent of third to sixth graders were reading at or above grade level; last year, the number was 47 percent.
But the other driver, officials said, is the comprehensive art program. Students cycle through music/drama, dance, Spanish, and phys ed, and in middle school can pick a "major." Even in core subjects, teachers incorporate art into almost every lesson.
"They're learning to think creatively and critically," Watts said.
The school was founded in 2008 by John Alston, a Swarthmore College professor and director of the 140-voice Chester Children's Chorus, as a private-public partnership with the school district.
Three years later, the distressed district cut staff after state funding reductions. CCSA's original charter application was denied - the reason being it would be too much of a financial drain on the district, Watts said - but the state Charter School Appeal Board overturned the decision in 2012.
Today, the school gets a boost from its fund-raising arm, the Chester Fund for Education, which raises from $600,000 to $750,000 a year.
"We manage to get a lot of what our children need," Watts said on a tour of the school, off Concord Road in Chester Township.
The location - in an industrial park where 18-wheel semis rumble by and a Frito-Lay warehouse is across the street - is the biggest surprise about the school.
Aside from the trucks, Watts said, "it's kind of quiet." Since most of the children are bused, there aren't too many parents at drop-off and pickup. And she described the play area out back as surrounded by a "swamp" because of poor drainage.
But inside, the school boasts a fully equipped art studio run by a master carpenter who also is a certified math teacher, a newly renovated gym, a cafeteria, and large classrooms big enough for dance classes or plays.
Asked what they liked about the school, a trio of seventh- and eighth-grade girl dancers said in unison, "Everything."
"It's a different environment," said Rahnaezeh McDonald, 14. "We dance, but we learn about music and other dancers. It's so amazing."
Students at CCSA.
CCSA's 2014 School Performance Profile, best
in the district.
Students reading at or above grade level, up from 36% three years ago.