You can apply both multi-class and multi-student discounts using Transactions > Post Tuition Fees by ensuring that If Family / Acct is eligible for both multi-class and multi-student discounts, should they get both? = Yes. (Make sure your organization wants this! If your organization uses Tuition Discounts, this doubles your discounting.) If this is answered No, only multi-class discounting is applied.
Post Tuition Fees by Total Hours only offers Multi-Student discounting since the class discount is already built in.