Dear friends:
Drinking is not assur. One needs to drink, if they choose to, in a manner that is consistent with Torah values. Getting drunk does not cut it. People who cannot handle alcohol should also not drink at all. Those who lack the maturity to drink responsibly should also not touch it. With these values in place, it becomes incumbent on those in charge to establish guidelines that are more specific. So laws that create a minimum drinking age make sense, though there are undoubtedly some older that cannot handle the decision of when to stop. And perhaps there are some younger who have that maturity. The question here is about yeshiva bochurim. In the long run, making something assur for a group because of the dangers to a smaller proportion of that group is sensible. Do all bochurim who drink get drunk or drink to excess? I’m sure the answer is no. But every yeshiva should establish a rule that is enforced with consistency that protects the population of bochurim. Not because “drinking” is assur, but because there is no way to insure safety if it was allowed.
As to the age of maturity, developmental psychologists have stopped considering 18 year olds adults. Many consider adolescence as ending at 20, some later than that. Then there is a new stage of “young adulthood”, and this extends even farther into the 20’s. I’m not beholden to any of these stage theories. But the position that children mature at 18 is long obsolete, at least in the field of psychology.