It is an inverted way of saying: A union's annual conference will hear (that) schools must ensure blameless members of staff do not have their careers wrecked by false allegations. In other words, one of the conference speakers will give out that message.
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slocawberSo: it hasn't been given out yet.Yes. "will" is something that will happen (is planned) for the future. Perhaps the abstracts of the presentations have been released, so the content is already known.