Historical clue formulations

• When you're about as smart as a fifth grader — 2021-11-28
• When many kids start fifth grade — 2018-02-01
• What Bart Simpson has been since 1989 — 2016-11-20
• When many verge on adolescence — 2015-09-17
• When Tatum O'Neal won her Oscar — 2014-06-29
• What many fifth graders have reached — 2009-06-03
• Threshold for the Vienna Boys' Choir — 2005-11-03