An interesting site and interesting article
I found this article about how the "math is not for girls" prejudice
is already present since second grade (in the US, the situation is
different across countries):
It cites a website called project implicit that has some interesting tests:
The tests consists mainly in checking how the speed of sorting words
into categories changes when two categories (like math and girls in
the above example) are on the same side or on different sides.
I had visited it last year and complained that it was all in English,
and thus sometimes it was hard to sort correctly for a non-native.
Now they have some localized tests in Spanish, although there are many
more in the English site (I didn't check other languages).
It's not that it will reveal something completely unexpected, but it
might help uncover some hidden biases.