| 100% | USCENSUS | 8 | Once-per-decade count tabulated on the first day of April (and certainly not a prank) |
| 37% | PEAR | 4 | On the first day of Christmas, your true love may send you a partridge in this "poached fruit" tree |
| 35% | JOANBAEZ | 8 | *Singer on the first day of Woodstock |
| 35% | SHANATOVA | 9 | Greeting on the first day of Tishri |
| 35% | ASHES | 5 | Symbol on the first day of Lent |
| 34% | ASHES | 5 | Symbol bestowed on the first day of Lent |
| 34% | PARTRIDGE | 9 | Bird given on the first day of Christmas |
| 34% | ASHES | 5 | They're bestowed on the first day of Lent |
| 34% | SYLLABUS | 8 | Professor's handout on the first day of class |
| 34% | TREE | 4 | "On the first day of Christmas, my true love sent to me, a partridge in a pear ___..." |
| 34% | RAVI | 4 | He performed before Melanie on the first day of Woodstock |
| 33% | SHY | 3 | Having trouble making friends on the first day of school, say |
| 33% | ADVENT | 6 | & 18D First day of the liturgical year in Western Christianity, falling on any date between November 27 and December 3 |
| 33% | TET | 3 | Vietnamese New Year, celebrated on the first day of the Lunar calendar |
| 33% | RENT | 4 | Payment that's often due on the first day of each month |
| 33% | APRIL | 5 | A lot of pranks happen on its first day |
| 32% | MONEY | 5 | Remember the first time you counted your coins and bought yourself a popsicle with your pocket ___ (allowance)? Best. Day. Ever! |
| 32% | BUTWHYCANTIWEARIT | 17 | ...on the first day of school |
| 32% | ATO | 3 | Words on the first of a set, perhaps |
| 32% | TAKEITTOTHEBANK | 15 | "You can count on that!," and a hint to the starts of 16-, 25-, and 43-Across |
| 31% | NEWKID | 6 | Object of curiosity on the first day of school |
| 31% | LABOR | 5 | Day celebrated on the first Monday of September |
| 31% | PARTY | 5 | Remember the first time you received a birthday ___ (celebration) invite with your name on it and couldn't wait to go? Best. Day. Ever! |
| 31% | OKA | 3 | Site of a 78 day, 1990 armed standoff in Quebec between the Mohawk First Nation and the Government of Quebec |
| 31% | SENTTO | 6 | “On the first day of Christmas, my true love ___ me ... ” |
| 30% | WILLIAM | 7 | ___ Faulkner, author of "The Sound and the Fury" who once wrote the entire outline to a novel on his office walls |
| 30% | KICKME | 6 | Words on the back of a prank victim |
| 30% | DREWBLOOD | 9 | What the vampires did on the first day of art class? |
| 30% | DONALD | 6 | The first name of a Disney Duck and a US president |