This is what the letter said:

Dear Student:
Thank you for your recent note, and for sharing your thoughts with me. Your kind words echo the messages of millions of Americans who have welcomed me and my family to the White House with an outpouring of goodwill.

On January 20th, Americans spoke with one voice, choosing hope over fear, unity of purpose over conflict and discord. Our Nation faces serious challenges, but we will overcome them if our imagination is joined to common purpose.

Now is our time to reaffirm our enduring spirit, and choose our better history. With your help, we will renew our Nation's promise to carry forth the great gift of freedom to future generations, as our forbears have delivered it to us.

Sincerely,
Barack Obama