Final answer:
The minimum number of formal teacher observations is not universally fixed, but at least two per teacher can be beneficial, particularly in teacher-artist collaboration contexts or similar educational programs.
Step-by-step explanation:
The minimum number of formal observations a teacher must have can vary based on the educational institution's requirements or the specific program goals.
However, in the context of support for classroom teachers in collaborations, such as a teacher-artist collaboration, it's often beneficial to conduct at least two observations for each teacher to effectively assess the engagement and effectiveness of the collaboration. The observations are essential to ensure the implementation is successful and provides the insightful feedback necessary for teacher growth and improving classroom practice.