summer melt
n.— «Bryant said that, typically, some students change their minds during the summer. However, he said, he is confident that the university will not lose significant numbers to what he calls “summer melt.”» —“SMU Expects Entering Fall Class To Be ’86 Size” by Connie Pryzant Dallas Morning News (Texas) June 25, 1987. (source: Double-Tongued Dictionary)
Further reading
Amid court-ordered busing in the 1970s, a middle-school teacher tried to distract her nervous students on the first day of class with this strange assignment: find a monarch caterpillar. The result? A memorable lesson in the miracle of metamorphosis...
A Dallas, Texas, woman and her friends often use the expression All the things to mean something like and whatnot or as a way to signal a kind of mutual understanding, suggesting something similar to the phrase you know. This sense probably comes...