Not necessarily. The hard, cold fact that actually disturbed Miss Giddens was that the children, especially Miles, were no longer innocent. They had been psychologically scarred by witnessing the overtly sexual relationship between Miss Jessel and Quint. The undertone in the film is that Miles was attempting to replicate the sexual behaviour he had observed, not only with Miss Giddens, but also with Flora. That is a shocking prospect for anyone - even modern audiences - to consider. Because Miss Giddens couldn't bring herself to attribute such terrible motives to children, she blamed it on supernatural possession.
I think the film is a study of the psychological impact of sexuality, and how repressed sexuality (as seen in Miss Giddens) is as dangerous as overt sexuality (as between Miss Jessels and Quint). A more worldly-wise governess might have consulted psychologists to save the children instead of attempting to exorcise the spirits.
Great comments, Rex16.