Training age

[Dalton Clark]

It's probably crude and I apologise in advance but I've told my boy when he has hair above his wang, he can come lift weights.

This is exactly what Rip means when he says boys can begin training when they enter Tanner Stage 4 - of which you specified the primary characteristic of that stage.

[Charlie Davies]

The problem with training kids is that few of them are very disciplined.

You can coach most 11-14 year old kids into decent form, depending on their level of coordination and your coaching skills, if you catch them in a moment of enthusiasm.
And they can put on muscle, though not like an older teen.
But it's a very unusual 12-year-old who will lift consistently as a volunteer.

If you have such a kid, that's awesome.
But if your kids are as flaky as mine have all been at that age, you'd have to be pretty harsh on them to get them to follow SSLP for more than a week or two. Bordering on abusive.

[GammaFlat]

he is 12. What would be an appropriate age to start the program? He has not gone thru puberty

My son started at age 12 and I believe he was tanner stage IV... and yeah, look it up.. I don't want to talk about it.
I believe that stage IV is required for the correct balance of testosterone mostly but older helps with ability to focus and tenacity. I feel very fortunate in that my kid can focus and he's willing to listen to me.

There are many posts about coaching family members and it seems to rarely go well. Don't beat yourself up if it doesn't but here's a tip: use a "rearranged" authority model where you're not really the boss. Send authority up the food chain.. "Book says.." Or "Rippetoe says.." whenever you sense pushback. Try to be on top of his feelings so you know when to throw in the cue. If he has mentally bought into the system use that! You thus avoid the natural teen/parent standoff.