Setting a high expectation begins the process of building up their self esteem. The writing assignment demonstrates that I am interested in them as individuals and would like to establish different lines of communication. Once the shock wears off they really get into the writing and describe their innermost feelings about their anxieties. A word of caution is appropriate here. A few students may react negatively.
Some students miss the humor of the letter because they are so overwhelmed with anxiety.
Often they will call to discuss their concerns and I can reassure them that they are not being asked to learn algebra on their own, quite the contrary, we will all be working very hard together. Some students are aware of cooperative learning teaching techniques and prefer lectures. They have a chance to switch classes without losing any class time or they can attend a class or two on a trial basis while still being prepared to switch. Once I get them in class however they never do switch. With their autobiography in hand and a healthy curiosity they arrive at the first class.