I have over 600 students in my school. Not too many by modern standards, but a lot of computer users for one guy to manage part time. In a corporate environment, dedicated IT staff would certainly maintain individual network accounts for every user in the enterprise, but is it worth the effort to create and maintain accounts for all students in a K-12 environment? In the corporate world (or even at a college or university level), the need for security, shared file access, and network storage is a paramount. However, the top priority at the K-12 level is Internet access, which certainly doesn't require an individual user account.
So why should I (or any of us in the same boat) expend the time required to manage accounts for students (regardless of network operating system)? In my experience, the alternative (effectively "guest" logins or open terminals) is acceptable for many students, but becomes problematic when a student takes a course requiring computer use or needs to protect his or her work. For example, our state standardized testing allows special education students to type responses to many questions using a word processor. If students are using public terminals, then their saved responses are easily accessible to other students. Similarly, general logins in a classroom setting lend themselves to cheating and sabotage, significantly hindering in-class activities and interfering with teacher-student interaction.
When I rolled out individual student logins for just those users enrolled in a few of our computer classes, student complaints about loss of files immediately dropped to nothing. My web design class in particular had managed to develop a signficant rivalry with my introduction to computers class and the students took great pleasure in deleting or modifying each others' files between classes. Individual logins immediately ended this problem and also allowed me to better track long-term projects stored on the computers for each class. Implementing the logins also allowed me to offer network storage to each user. Files stored on the network are backed up nightly and tend to be quite a bit safer from equipment failure than those stored locally on our 7-year old donated hard drives. The only computer teacher whose classes were not assigned individual accounts on the network made me promise to provide her with the same functionality next fall (her Excel and Word classes have developed a bizarre rivalry second only to that of my two classes).
And thus, I may as well provide network accounts for all potential computer users in the school. Most students will at some point take a course requiring computer facilities. Since all of our facilities are shared (I think most of us have agreed that shared desktops are a vastly better use of limited funds than dedicated and underutilized laptops), even students who want to type a paper over a couple of days could obviously benefit from secure network storage. In the end, in fact, the upfront effort of creating accounts for all students is most likely insignificant compared to the management required to create accounts on a class-by-class basis or the headaches that students and teachers experience in a shared, unsecured environment.