In a discussion on contrivances, the subject of sex education (really just anatomy education) the subject of drawings versus photos was discussed. In the Will McBride book, photos were used but given that these are actual children, using their bodies in an illustrative text might be stigmatic and ethically questionable. The most obvious solution is to use realistic (and accurate) drawings. That way, the particular personality of the child would not be identified as some real person even if there was a life model originally. The amusing bit is that with the English-speaking world’s discomfort with frank presentations of the naked body, many books have become overly cartoonish, offering little useful detail. Ladybird Books was cited to by a number of readers as a good exception. Your Body was published in 1967 and a blogger (The Serendipity Project) took the trouble to scan its contents.
Interestingly, one of the other images in that book shows a family at the beach and guess what? The little girl is wearing no top! Yet another can of worms that has been discussed on this site regarding the convention of topless girl children on public beaches.