I suggest straying from Imagine, unless of course you can provide a very original and insightful analysis. If you're looking for a song that has probably never been used in an HSC essay, try The Wanderer by U2. I used it in an assessment early last year and got full marks.
Lyrics:
I went out walking
Through streets paved with gold
Lifted some stones
Saw the skin and bones
Of a city without a soul
I went out walking
Under an atomic sky
Where the ground won't turn
And the rain it burns
Like the tears when I said goodbye
Yeah I went with nothing
Nothing but the thought of you
I went wandering
I went drifting
Through the capitals of tin
Where men can't walk
Or freely talk
And sons turn their fathers in
I stopped outside a church house
Where the citizens like to sit
They say they want the kingdom
But they don't want God in it
I went out riding
Down that old eight lane
I passed by a thousand signs
Looking for my own name
I went with nothing
But the thought you'd be there too
Looking for you
I went out there
In search of experience
To taste and to touch
And to feel as much
As a man can
Before he repents
I went out searching
Looking for one good man
A spirit who would not bend or break
Who would sit at his father's right hand
I went out walking
With a bible and a gun
The word of God lay heavy on my heart
I was sure I was the one
Now Jesus, don't you wait up
Jesus, I'll be home soon
Yeah I went out for the papers
Told her I'd be back by noon
Yeah I left with nothing
But the thought you'd be there too
Looking for you
Yeah I left with nothing
Nothing but the thought of you
I went wandering
If you do a little bit of research (which you should anyway, for all your texts) and a bit of metaphysical pondering, there is a lot of stuff you can draw from these lyrics. There's an abundance of biblical allusion in particular.