No
For those that prefer a longer post, no they should not.
But generally, no.
(At 5, we were changing for the swimming pool in mixed classes. Yeah, in the classrooms in front of everyone. People have got so obsessed with the idea that people might be looking at them that they're bringing in rules that will just accentuate pregnancies. From 14 kids are able to reproduce, and in a number of places in the world, they do. (Romeo and Juliet were about 14) That doesn't mean you destroy a child's position of learning by bringing in overprejudiced shit that they don't need to know yet.)
What they really need to bring in at 5 is "How to treat people with respect", that would do a hell of a lot more use than some stupid Pin A goes in Slot B shit.
Oh, Sex education for me?
Age 8: Don't hit guys between the legs.
Age 12: Here's a set of breasts and a wang. (The other part wasn't mentioned)
Age 14: Here's how to do a castration.
That's my total "schooled" education that I remember.
Unschooled...me and a certain girl had already been caught trying to figure it out at age 6...Damn, that caused a shitstorm.