Today is the fourth thursday of April, which is national Take Our Daughters and Sons to Work Day. The main Microsoft campus is not participating today, but there's a good reason for this.
The Washington State Assessment of Student Learning, better known as the WASL (pronounced "WAH-s'l"), is a four-day battery of standardized tests administered to all elementary school and high school students starting from grade 3. You can download sample tests and answer keys for the reading and mathematics sections of the test to see whether you would have passed high school had you gone to school in Washington. (Sample questions for other grades are also available, including calibration samples for the writing test.)
The problem is that the WASL is administered... at the end of April. Elementary schools have some discretion in choosing exactly which days they administer the test, and if they happen to choose a date that conflicts with Take Our Daughters and Sons to Work Day, then children in that school district are unable to participate in the event. Microsoft employees indicated that they would prefer to have the event in the summer to avoid the schedule conflict.