If the age goes up the same problems will persist. Look how well the age limit works on under18's for example.
Rather than trying to change the law to make the job easier and shift the blame the police should combat the anti-social behaviour itself. I think almost everyone has a group of drunks outside their local off licence, increasing the drinking age wont change that. Having a van full of coppers turn up and arrest them for drunk and disorderly a few nights running will stop most of them.
That's how they did it round here and my mum walks around here gone 11 often, never has a spot of trouble, because they've all either found something better to do or somewhere better to drink, like indoors
It only took a 2 week crackdown as they called it. Just just went from offy to offy, moving people along and carting people off dependant on their attitude.
Laws don't work, policing works. Quoted from the lovely PC Brown. One of the local bobbies who's actually a nice guy.