Students enrolling in first year Computer Science at the University of
the Witwatersrand differ in their level of programming experience. In
particular many of them have done programming in Pascal at high
school, while others have never programmed before.  In 1999 the School 
revised its first year curriculum and among other changes Scheme was
introduced into the curriculum in an attempt to reduce the
performance gap between students with prior programming experience and
those without programming experience. An examination of the
effectiveness of Scheme in reducing this performance gap, in the 2005
class, showed a statistically significant performance difference
between students with prior programming experience and those without
in the first two topics of the first year curriculum. Further
investigation revealed that the biggest difference occurred in those
parts of the course which required the students to think in an
imperative style while there was little difference in the parts of the
course which deal with algorithms or programs in a functional
style and also those parts that are more mathematical.