If you would like to model private school tuition, navigate to the Profile > Goals section, click Add Goal, hover over Education, and select Pre-college. Input the applicable years and tuition amount. Any education savings accounts that are listed in the Net Worth will pay out $10,000 per year for private school costs.
If you do not see the education savings accounts paying out for pre-college goals, make sure that the "Use 529 accounts to fund Pre-College Education goals" setting is checked in the Gear Icon > Settings > Methodology tab of your client plan.