It should also be possible to control this type of activity from
/etc/profile which is read before the
/home/user/.profile and is owned by root. (See: http://bash.cyberciti.biz/guide/Startup_scripts).
However, this would not prevent the issue of opening up another xterm or a second user logging in at the same time. If the system is not multi-user, i.e. there is only one user active at a time, then you should be able to get the desired effects of clearing the home directory by using
.bash_logout. (see: Create a logoff script/task for Linux)
To ensure that users don't edit these files make sure that they do not have access to
chmod. If they do not have access to these commands and the file has some restrictive permissions set say
0440 and is owned by a different user, then the files should be secure enough to prevent tampering.