[Orgmode] Call org-map-entries just on children?

[Richard Lawrence]

Hi all,

I'm sure I'm just being thick here, but any help would be appreciated...

I want to call org-map-entries in a way that calls a function at each
*child* of the current tree, but not at the current tree itself.  That
is, for some function f, if my Org file looks like this:

* Paper 1
** Student 1
** Student 2
...

I want to call f at "Student 1", "Student 2", etc. but not at "Paper 1".
But if point is positioned at "Paper 1", then

(org-map-entries 'f nil 'tree)

first calls f at the "Paper 1" entry, not the "Student 1" entry.  How
can I apply f just to the *children* of "Paper 1"?

(The reason I need to do this is that f needs to enforce that each of
the children has a value for a certain property, but the parent entry
should not have this property.)

Thanks!

Richard