Workgroup access denied for users and power users

Hello, I am an parttime IT-manager in a school and we are
experiencing some problems with our windows XP workgroups.
We have set up in three separate classes a workgroup of
about 20 computers, with on each computer three
useraccounts: administrator, teacher (poweruser) and
student(user). The computers were cloned so the accounts
are identically configured. When we log on as
administrator the sharing works just fine and we can
browse through the workgroup seeing all the computers in
the classroom. However when we log on as a student or as e
teacher, we get the message: workgroup access denied.
However when we search for a specific computer, we can
find it and access its resources (even when running the
most restricted account student), but we can not get tot
it through the workgroup icon, which is what our students
are used to in classes that run windows 98. So basically
the question is how do we enable power users and users to
browse the workgroup.