April
20th
- 1999 – Eric Harris and Dylan Klebold embarks on a shooting rampage at Columbine High School, killing 12 students and a teacher, as well as wounding 23 others, before committing suicide. It is the fourth-deadliest school killing in United States history.
23rd
- 1635 – Boston Latin School, the oldest public school in the United States, is founded in Boston, Massachusetts
25th
- 1983 – American schoolgirl Samantha Smith is invited to visit the Soviet Union by its leader Yuri Andropov after he reads a letter in which she expresses fears about nuclear war.