Reliable wireless starts with requirements, not access-point count.
Capacity
Estimate concurrent users and applications by area. A dense classroom or auditorium requires a different design from a small office.
RF environment
Consider channel planning, transmit power, building materials and sources of interference.
Security
Use appropriate authentication, segmentation and guest access controls. Wireless should be treated as part of the enterprise network security model.
This article is general technical guidance. Actual architecture should be validated against the organization's requirements, risk profile and existing infrastructure.