How can I alter the parameter nls_sort

I used "alter system set nls_sort = binary_ci scope = spfile" to
change the default value of the parameter nls_sort.Then I restarted
the service of the database instance.I saw the instance value has
changed.Now the problem is when I create a new connection the value of
nls_sort was not binary_ci but binary.I don't know why the session
value was not changed.

any advice will be appreciated!

Thanks a lot
Jack.Lee