Obama girls’ first day of school

Sasha peers out the window of a Secret Service vehicle on her first day of school Monday.  (Karen Bleier / AFP/Getty Images)

Michelle Obama walks Sasha to class on the Sidwell Friends campus.  (Jacquelyn Martin / Associated Press)

The Sidwell school, which marked its 125th year in 2008, opened in 1883 with 18 students.  (Brendan Smialowski / Getty Images)

Sidwell has been called “the Harvard of Washington’s private schools.” Its alumni include not only Chelsea Clinton and Tricia Nixon but also TV journalist Charles Gibson and Bill Nye, “the Science Guy.”  (Brendan Smialowski / Getty Images)