What do your children see at Art Galleries?

I have no issue at all with my children looking at art which reflects the underlying sexism of the society in which it was created (although I think the particular picture OP has picked is much more complex than that and as much to do with gods and mortals and the the whole chain of events set off by this choice- valuing beauty above all turned out to be disastrous, but that's another thread) provided they can learn to engage intelligently and think about what the picture means.

I'd be thrilled if they were currently in the National Gallery looking at Rubens rather than in an exam hall.

You could balance it if you wanted by looking at how some of the female painters from the Renaissance etc depicted famous scenes and how that differed to the male gaze. You could also talk about why there were less female painters than men and how they were obscurified over time. There's lots of lessons you could give without blocking access to art.

Alternative answers:
-Paris is an idiot who given a choice between wisdom, strength or having the prettiest wife chose the latter. Thus causing no end of trouble for everyone
-Eris would probably start angry threads about weddings on AIBU if she was around now
-beauty standards/the ideal body change a lot with time

rubens was a wonderful painter. I don't agree with censoring the past. Even if it contained some dodgy attitudes

The message is probably that the world was a very sexist place in the past and that women are all too often depicted in sexualised contexts because they are painted by men. And that in some aspects, not much has changed. Look at the sexualisation of girls and women today. It is important to acknowledge it and to understand that while there is still sexism in various degrees in the world, that hopefully your daughter will still thrive. And that there is no one way to be a woman or a man.

That we are but the playthings of the gods, even kings dependant on their fickle whims?