When Should Sex Education Commence?

I would have thought - maybe around age 13 or 14. Hence I was somewhat surprised to read this in the regular parents' newsletter from my kids' kindergarten/preschool:

"Birds & Bees - It is natural for K2 and primary school children to start wondering about where they came from and how babies are made. At [name of school deleted], we introduce sex education to our K2 students, explaining the scientifically complex and wondrous processes of human conception and birth in ways that are appropriate for young children's understanding. It is important for us to demystify or clarify any misconceptions that young children may have about these topics."

But I have confidence that this school will do a good job at teaching this topic. I've been very happy with the high quality of education provided by this school so far. They teach at quite an advanced level for all their kids who attend the different classes (three to six years old), but the lessons are always done in a fun, enjoyable way and all the kids generally seem to be very happy. Plenty of games, hands-on projects, field trips, artwork and so on. Some other stuff that the K2 kids are doing this term:

"We will take a closer look at human cells, genes, DNA and chromosomes, and understand what determines a baby's gender. For social studies, children will be inspired by the life stories and incredible achievements of sports personalities like Lance Armstrong (cancer survivor and world cycling hero), Terry Fox (disabled cross-country runner and founder of Marathon for Hope), Nadia Comaneci (world's youngest Olympic gymnastics winner at age 13 and devoted to charity work today) and Tiger Woods (overcame racial discrimination to become a world golfing champion."

I've decided not to mention the name of the school, because I don't want them to get into any trouble with the Ministry of Education for using an "age-inappropriate" syllabus (they may not, but why take the chance). Personally, I don't think I knew what a chromosome was, until I was fifteen years old and had to study that one solitary chapter on genetics, in the Lam Peng Kwan textbook for O-level Biology.