Man and boy stood cheering by, And home we brought you shoulder-high. (3-4)
The poem's first stanza ends with the speaker remembering a celebration after a big race. The victorious athlete is deposited safe at home by his adoring fans. Sweet. We can imagine a few final high-fives at the doorway, and then the athlete heads inside to unwind after a tough day of kicking tail and taking names. You know what they say—a young athlete's home is his castle.
Today, the road all runners come, Shoulder-high we bring you home, (5-6)
Things take a turn in the second stanza. We jump from the nice memory of the athlete arriving home on the shoulders of his adoring fans, victorious after the big race, to the athlete's casket being carried to his gravesite on the shoulders of the pallbearers.
The phrase "shoulder-high," is repeated from stanza 1. The word "home" is also repeated. It seems pretty clear that Housman wants us to make a connection between home in the first stanza and home in the second.
Housman wants some of those warm, happy feelings of home from the first stanza to comfort us as we are confronted with the sadness of the athlete's untimely death in the second stanza. A.E. was super-considerate that way.
To set you at your threshold down, Townsman of a stiller town. (7-8)
It's the athlete's new home all right. They set him down right at his front door—well actually the threshold here is probably more like an open grave or tomb. Still, Housman wants us thinking about this in the sense of returning home, which has a nice, comforting ring to it, right?
And there's even more good (good?) news. Even though the athlete is dead and heading to his new "home," he isn't going to be alone. Isn't that great? He's going to be part of a town, a community. Sure, the town is a cemetery and all the residents are dead, but it's a nicer way to think about it than just sticking a cold, dead body in the ground next to a bunch of other dead bodies. Not nice.