At the same time, the only thing keeping him a moisture farmer was Uncle Owen. All his friends joined the imperial academy to become a pilot, which is what he wanted. He could have easily decided that was the path to take, but his choice fell to the greater good to become something more. Feels like a vital choice to me. One putting him on the side of the empire, the other a rebel.
I'm (definitely) not a Starwars fanboi, but I believe Biggs, one of his friends, went to the academy...and turned up with the rebels as a pilot, so I'm not sure it was such a black and white choice as you've presented. Plus Luke states explicitly that he 'hates the Empire' so I'm not sure this academy was really part of the Imperial Navy/Army system.
However I still disagree, the choice was made for him by the plot. He did hum and haw before much had really happened. First he agreed to stay for another year when everything was very ordinary and humdrum, then he got all these new shenanigans confusing the issue. So what did he decide...
...well, he fudged it a teeny bit at first, but offering some lukewarm help for Ben Kenobi in offering to take him to Anchorhead, but then I doubt he would have, over the smouldering bodies of his aunt and uncle decided, 'you know what, I'll still enrol in the academy as I originally wanted to' or 'those condensers on the South ridge ain't going to look after themselves'. So in my mind, with respect to the plot given to us, he only had one path forward and no choice.