First find how many students go to the new school: 1590 students * .4 = <<1590*.4=636>>636 students
Then divide that number by 3 to find how many students are at each grade level: 636 students / 3 grades = <<636/3=212>>212 students/grade
Then subtract the 20 students in the gifted class: 212 students - 20 students = <<212-20=192>>192 students
Then divide that number by 6 to find the number of students in each other class: 192 students / 6 classes = <<192/6=32>>32 students/class
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