My answer to that depends on what brand of manifestation would be taught.
Most LOA books teach a type of manifestation that is completely detached from any kind of value or belief system. In my opinion, when you do that, thereby leaving people without moral guidelines, you encourage them to become selfish pricks who will only chase after more toys, more riches, and more instant gratification.
When you teach our kids Service to Self instead of Service to Others... if you teach them that should have faith only in the government and in themselves, and that God either doesn't exist or is some amorphous Amazon in the sky called "The Universe"... you put them on the road to Hell.
So if you told me to teach our youngsters manifestation, I’d start by telling them about Jesus. Next I would tell them that the reason we’re all here is to know, love, and serve God.
Here's another important lesson: We are all sinners. I know, that's a tough pill to swallow for a New Ager. I've been there. But just because you don't want to hear it doesn't make it any less true.
Or how about this: Life isn't supposed to be easy. Growth only comes through challenge.
Your soul is like a raw gemstone. God throws it into a tumbler and watches it bounce around until it has lost the rough edges and is polished and shiny and smooth. The end goal is turn you into the best possible version of yourself.
Some of us are being taken through a special process, being hand-selected and cut and polished over and over. If they don’t break, they’ll emerge as an exquisite, sparkling jewel. These precious souls are called saints.
Those are the people who triumph over especially tough circumstances in their lives and come out the other end as teachers for mankind and an inspiration for everyone they meet.
You don’t get that by scrambling to keep up with the Joneses, or making it your life’s goal to own a private plane.