#### Figure 1: Absences, Course Grades, and Test Score Growth by Math and English Period.

Six panels. Panel A: Math Absences by Math Period. Panel A shows three lines, each of which plots average absences in math courses through an entire school year over the first seven periods of the school day. The three lines in this panel three mutually exclusive race and ethnicity groups: black, white, and Hispanic (as defined by the Chicago Public Schools). The solid line shows absences by black students over the course of the school day, the dashed line shows absences by white students over the course of the school day, and the dotted line shows absences by Hispanic students over the course of the school day. For all three race and ethnicity groups, absences in math classes are higher in first period than in any other period: for black students the average is 35.1, for white students the average is 28.9, and for Hispanic students the average is 28.6. The pattern of absences follows a "U" shape for each group: absences steadily decline until fourth period and then steadily increase until the end of the day, though first period remains the period of highest absences. In Panel B this exercise
is repeated for English course absences; the title of Panel B is English Absences by English Period. Panel B again shows three lines, each of which plots average absences in English courses through an entire school year over the first seven periods of the school day. The three lines again represent
three mutually exclusive race and ethnicity groups: black, white, and Hispanic. As with math courses, absences are highest in first period: black students (represented again with a solid line) are absent an average of 32.1 times per year, white students (represented again with a dashed line) are
absent an average of 26.4 times and Hispanic students (represented again with a dotted line) are absent an average of 26.6 times per year. Again, as in Panel A, the pattern of absences follows a "U" shape for each group: absences steadily decline until third period and then steadily increase
until the end of the day, though first period remains the period of highest absences. Panel C: Math Grade by Math Period. In Panel C, the average course grade is traced through the course of the school day for the same three race and ethnicity groups as in Panels A and B. Course grades are
translated from letter grades to numbers: an A is equal to 4, a B is equal to 3, a C is equal to 2, a D is equal to 1 and an F is equal to 0 grade points. Again, black students are represented with a solid line, white students are represented with a dashed line, and Hispanic students are
represented with a dotted line. In this panel, each of the three lines have an "upside-down-U" shape, where course grades are lowest at the beginning of the day in first period, then gradually rise until the middle periods of the day, after which the grades steadily fall. Course grade are lowest
in first period (1.34 for black students, 1.55 for Hispanic students, and 1.71 for white students). White and Hispanic students have their highest in fourth period (1.81 and 1.69, respectively) while black students see the highest average math grade in 3

^{rd} period (1.52). Grades steadily fall from their mid-day peak for each group. By seventh period, the average grades are 1.76 for white students, 1.60 for Hispanic students, and 1.40 for black students. Panel D: English Grade by
English Period. In Panel D, the Panel C exercise is repeated for English classes: the average course grade is traced through the course of the school day for the same three race and ethnicity groups. Again, black students are represented with a solid line, white students are represented with a
dashed line, and Hispanic students are represented with a dotted line. In this panel, each of the three lines have an "upside-down-U" shape, where course grades are low at the beginning of the day in first period, then gradually rise until the middle periods of the day, after which the grades
steadily fall. Black and Hispanic students both see the lowest English grades of the day in first period (1.65 and 1.82, respectively) and highest grades in third period (1.83 and 1.92, respectively); by seven period, grades have fallen to 1.67 and 1.82, respectively. White students have an average
first period grade of 2.02, third period grades of 2.10, and seventh period of 1.96. Though the trend of grades over the course of the day is similar to black and Hispanic students, the white students actually see lower average grades in sixth and seventh period than in first period. Panel E: Math
Test Score Growth by Math Period. In Panel E the test score growth is computed as the change from fall term to spring term in the classroom's average z-scores of a math standardized test score. Again, black students are represented with a solid line, white students are represented with a dashed
line, and Hispanic students are represented with a dotted line. No discernable pattern is seen over the course of the day. Panel F: Reading Test Score Growth by English Period. In Panel F the test score growth is computed as the change from fall term to spring term in the classroom's average
z-scores of a Reading standardized test score. Again, black students are represented with a solid line, white students are represented with a dashed line, and Hispanic students are represented with a dotted line. No discernable pattern is seen over the course of the day, though it appears that
black and white students in later periods of the day see higher test score growth than in earlier periods of the day.