Oh back off mama! Can you imagine your dad wanting to talk to you about your period? Ick, right? That's what he's thinking. If you're in a decent public school system, they've already covered this, probably 2-3 years ago. Honestly you're way behind if you're trying to talk to him about puberty. Assume he's already figured out what he needs to know from health class at school and his friends and leave him alone.
What you will need to be able to talk to him about is your family values regarding dating and relationships. School can teach him about puberty, pubic hair, wet dreams, erections, hygiene, voice changes, growth spurts, acne, body odor, etc. They will also cover the basics of reproduction and, depending on where you live, birth control. They will teach them that no means no and dating violence is not OK, about sexting and using the internet. It will be up to you to open the lines of communication about what you expect regarding what is OK and at what age regarding relationships and sex. Things like hickeys, "feeling up" and oral sex happen way earlier that you think, and those are the conversations you need to have early.