private directories

I am trying to create a directory that can only be read by 1 group. The
problem is that now that directory can only be seen if checked out
explicitly.

i.e.
svn co http://svn/test/trunk
A trunk/test.txt
Checked out revision 5.

svn co http://svn/test/trunk/secret
A secret/test.txt
Checked out revision 5.

Is this a bug or a feature? My ACL file follows.

[groups]
dba = dnewman

[/]
# Allow everyone read on the entire repository
* = r
@dba = rw

[/trunk/secret]
* =
@dba = rw