Yes, if they are given LOCAL administrator rights to the workstations, they can log off other users. By default, an assigned user has local admin rights to their workstation, so this is not a huge deviation from the norm.
However, if you are interested in further restricting these users, you can easily do so... even if they are members of the Local Admin group. You may want to consider Software Restriction Policies (inhibits installation of non-aproved software), which is generally the most problematic area when users have admin rights.
Jeff
TechSoEasy