the town I grew up in had a coupla choices for us under age'ers to try. Mostly white town.
One town away was mostly black ... both young and old bars.If ya went into one of the old man black bars, kept yer mouth generally shut, and tipped the bartender from the get go you could stay and sip your drafts in peace. The old guys would even warn you about going across the street, to the young block guys bar.
In our town, the best bet was to hit one of the mill bars with the younger crowd and hope to find a friend of my older brother ... sit next to him, offer to buy the next round ... then try your best to fit in.
Bars within walking distance to the front gates of the steel mills and foundry's wer the best bets at getting a beer. By 10th / 11th grade ... you could walk in and sit next to the kid that quit HS that year and went to work at the mill. The bartenders usually thought old enough to work the mill, old enough to drink a beer.