Collegial Conferences During Lessons?

When I'm involved in a lesson, even if I'm sitting apart from learners, I am actively watching, listening, and acting on what the students are doing.  If a colleague comes in to discuss another matter, I will usually request that we talk at another time because once my attention is taken from the learners,  my steady attention to the lesson/learning objectives drifts.

While the learning is taking place, and when I'm not interacting with students, I'm usually watching and assessing the following points:

• Is the lesson structure working?
• Were children able to transition successfully to independent/group work?
• Are the small groups working well together?
• What else do students need to successfully gain the concept, skill and/or knowledge?
• Who needs remediation, enrichment, more practice and review?

Many teachers flexibly confer and teach during the day.  Specialist teachers drop in to confer, pull students, and spontaneously alter the days' efforts.  While I recognize that there's a degree of flexibility that's necessary due to unexpected student events/needs, student/teacher absences, and needed redirection during a lesson, in general, I believe it's best if teachers have a solid schedule to follow, and most of the service delivery and learning facilitation happens without impromptu meetings and discussions during lesson delivery.  

What do you think?  Should elementary teachers be more flexible and willing to stop lessons to have short meetings/conferences with specialist teachers, parents and others who might drop by, or should we mainly redirect those meetings/mini-conferences to more thoughtful times and scheduled planning meetings?  This may sound like a minor matter, but when classroom teachers are working with many children at one time, and many colleagues throughout the week, it's important to preserve the time and space for optimal learning and meaningful, focused dialogue.