If so, is this limited to grades K-12?

It's hard for me to imagine a world where college students are drinking less (or where high school-educated 21 year olds are drinking less).

Is this measured in any ways other than self-reported polls?  (For example, are alcohol-related ER visits declining for college students and/or people aged 18-35?)

Gallup makes the following claim:

Young adults in the U.S. have become progressively less likely to use alcohol over the past two decades, with the percentages of 18- to 34-year-olds saying they ever drink, that they drank in the past week and that they sometimes drink more than they should all lower today.

Is this true?

It's hard for me to imagine a world where college students are drinking less (or where high school-educated 21 year olds are drinking less).

How is this measured?(For example, are alcohol-related ER visits declining for college students and/or people aged 18-35?)