Quarter of birth is a valid instrument for educational attainment because:

a.

Compulsory schooling laws mean that people born later in the year are forced to stay in school for longer than people born earlier in the year.

b.

Children born later in the year are more intelligent than children born earlier in the year.

c.

Children born later in the year can drop out of high school sooner than children born earlier in the year.

d.Children who start school at an older age experience a higher return to educational attainment.

e.

Parents invest more in children born later in the calendar year.