The results in preliminary assessments usually have no direct effect on HSC results, however the content of the HSC course is built on the preliminary course. That means the some contents of the preliminary course may be needed to do the HSC course. For example, in physics you may need to use a formula you have learnt in the preliminary course to do areas in the HSC course. The direct results from the preliminary course shouldn't affect the HSC course, but in terms of knowledge and understanding they may have an effect. However, I do believe that most schools would revise some areas of the preliminary course if it is needed for the HSC course.