Organising a Cross-Country
When creating a cross country carnival, set Athletics as the carnival type.
(In previous versions of SportsTrak, Cross Country was a separate carnival type to Swimming or Athletics. Its program only contained Cross Country events for each age and level. This was an annoying constraint for some schools as they wanted a few other event types in as well, so we have just got rid of that option. Athletics covers it now)
In the Library of Events, you require and event type of Cross-Country or similar name (Timed, Track, Normal)

Set up a Program of events with a Cross Country for each level and gender. Often this means 12 events.
Rather than A grade, I'd suggest X grade on the program because you will maybe want placings to go well beyond a typical A grade athletics event.
Scoring a Cross-Country
How to score a cross country can be a difficult decision. In the interests of scoring fairness every house should have the same number of contestants but this this can usually only be enforced in an Inter-school carnival. Within a school you want maximum participation and the numbers per house will always vary.
If you are not interested in overall house/team scores then the score system is essentially irrelevant because you are only interested in placings, which can be printed without requiring scores.
One approach to this problem is to only score the best few competitors per house, regardless of how many competitors there are per house.
Using Massed Entry with Cross Country
Add Cross Country as the event type in massed entry.
On the day, you require a place for the number of contestants that you want to record. Maybe it is all of them. Thus maybe you have a sheet upon which the placings are written manually at first.
When recording placings, do not bother trying to sort by age/gender. Just overall relative placings. As long as everyone in that age/gender group have the same starting time (even on a different day), those placings will identify the relative positions of each of those competitors.
You might record the Performance for the first handful of finishers, but after that there is usually no real need for this. Their relative placing is what matters.