In the context of SLA based job scheduling for high performance grid computing, this paper investigates the behaviour of various scheduling heuristics to schedule SLA-bounded jobs onto a parallel computing resource. The key objective of this investigation is to evaluate the effectiveness of simple scheduling heuristics using as criteria the maximization of resource utilization (both in terms of time and SLAs serviced) and income. Our results suggest how each SLA constraint ought to be prioritized in order to improve the income.