I remember a line from a poem which goes something like, "Show me your
son's friends, and I will tell you what kind of man he will become". 
I thought it was Rudyard Kipling, but perhaps I was thinking of "If". 
I would like the name of the poem and the poet.

The end of the poem IF by Rudyard Kipling does sound similar do the
poem you're looking for.

"If you can talk with crowds and keep your virtue, 
Or walk with kings - nor lose the common touch; 
If neither foes nor loving friends can hurt you; 
If all men count with you, but none too much; 
If you can fill the unforgiving minute 
With sixty seconds' worth of distance run - 
Yours is the Earth and everything that's in it, 
And - which is more - you'll be a Man my son!"