Ann Hassenpflug has an interesting article in this week's Chronicle of Higher Education  on the difficulty of teaching a graduate-level education class when parents whose childcare arrangements have fallen through bring their children to class. A lively and sometimes heated discussion follows in the comments.
Having been on three of the four "sides"of this issue (that is, I have been distracted by children in a classroom when I was trying to learn; I have taught a seminar and have conducted therapy sessions to which parents brought their children; and I have been forced to bring my own child to meetings and even group supervision sessions (as a supervisee), though my own parents never took me to work or school when I was a child), I feel sympathy for everyone involved.
It can be hard to maintain focus, as either a student or a teacher, when there is a child present. No matter how well behaved the child, most kids who are too young to be left unsupervised have limited tolerance for sitting silent for extended periods, and will eventually need to stretch their legs, use the bathroom, eat a snack, or merely initiate some human interaction.
It is even harder to be a parent trying to balance obligations to one's child and career. (And for many parents, earning a degree is a way of fulfilling the obligation to provide long-term financial security for the child.) As the working parents of a young child, Bill and often felt we were in a catch-22 situation when the best-laid childcare plans, including backup plans, disintegrated. One of us could miss work and be seen as unreliable, or bring Ben and inconvenience co-workers. It was a lose-lose proposition. (And we were lucky; there were two of us. Single parents not only have a thinner safety net, but are less likely to be able to afford reliable childcare to begin with.)
Which is why I don't think there is a private, interpersonal solution to the problem. It's not something that can be worked out between teacher and student, employer and employee.
As several commenters have pointed out, the student population is increasingly older and female. Many of these nontraditional students are parents. Students pay mandatory student services fees, but parents seldom get to take advantage of the services and activities that are geared toward younger, less encumbered students.
Similarly, the norm of a one-earner household is a thing of the past. Most parents need to work full-time regardless of their personal desire or political beliefs, and no matter what they thought when they decided to have children (if, indeed, it was a decision), functioning well as both a parent and an employee is difficult at best, and often impossible.
We need universities, corporations, and especially government agencies to acknowledge this reality. We need affordable, reliable daycare and emergency childcare, so that parents can make the optimum contribution to society. And if the erosion of contraceptive and abortion options continues, this need is going to become even more pressing.