A Center Controller reported their facility took over the airspace of two underlying TRACONs. The reporter stated Center Controllers have insufficient training and experience to work these types of airspace.

Narrative

This report is being filed to bring your attention back to a systemic safety issue within the FAA's contingency plan in reference to ZZZ [ARTCC] sectors taking over ZZZ [TRACON] and ZZZ1 [TRACON] airspace during limited services (ATC Zero) planned and unplanned events. I offer the safer resolution to rewrite the contingency plan to have the two adjoining approach controls share the responsibility for providing limited services to the users during ATC Zero events for ZZZ [TRACON] or ZZZ1 [TRACON].On Day 0 around XA:00; my area assumed ZZZ [TRACON] airspace for a planned ATC Zero event. The controller who ended up working through the left over traffic in ZZZ1's airspace was visibly shaken the next day as they were describing the stress they went through trying to keep things safe in an unfamiliar configuration. They mentioned the earlier start to the ATC Zero event left much more traffic than expected and the flight school was still actively pursuing services as if nothing was limited.I reached out to the ZZZ1 Supervisor and from that conversation I learned two things. The facility would normally schedule eight people at this time of the shift; just because of the high workload the flight school demands. Secondly; the Supervisor and the Facility Chief advised the flight school of the limited services planned for the evening but the Supervisor was not surprised to hear the flight school did not slow their operations or curtail their expectations towards ATC services. The Supervisor explained during other limited operations; such as our COVID schedule; this flight school disregarded the FAA's request to spread out their schedule in order to allow safer scheduling for the controllers shifts. One could deduce that these decisions are most likely not safety driven.I've already mentioned my recommendation and I realize the easy effort is to keep saying; 'we have addressed the issue with bi-annual training.' This is not the safest options for our users and for the sanity of our controllers. I've gone through the training and put effort towards understanding the foreign rules and procedures. I've also applied this training towards an ATC Zero event. Twice a year training for such an unpracticed skill should not be accepted as a safe remedy. The surrounding approaches should be made capable and are already much more practiced in the art of approach control services which is why they should be tasked with this duty during scheduled ATC Zero events.During a natural disaster; ATC Zero event where the surrounding approach controls have to evacuate; it makes sense to expect ZZZ [ARTCC] to provide very limited services.