"Spacing before" will not be suppressed if the "Page break before" option is
checked; instead, you will have to set the "Spacing before" to zero for the
style.
If "Page break before" is not part of the style definition, "Spacing before"
will be suppressed when the paragraph occurs at the top of a page (this does
not apply to the first page of a section, though, where the spacing is
always added).