Should my kid save, spend, or reinvest what they earn?

Three pots, and the order matters more than the percentages.

The float comes out first. The business needs money to keep running: fuel, supplies, the thing that wears out. That money is not profit and it never was. A kid who skips this step discovers it on a Saturday when there is no gas, which is an excellent lesson provided nobody rescues it.

Then reinvestment, if there is something worth buying. Not gear that would make the business feel more real. Gear that more customers are waiting on. The test is whether the purchase comes after demand or instead of it, and the arithmetic is how many jobs it takes to earn back.

What is left is theirs. Genuinely theirs, including the portion they will spend on something you find ridiculous.

That last part is where most families want to impose a rule, and it is worth resisting. A savings rule imposed on their money quietly reconverts it into your money with conditions attached, and the ownership was the entire point. Spending money badly is how anybody learns what money is worth, and eighty dollars at thirteen is the cheapest that lesson will ever be.

What works better than a rule is a question, asked once, without a preferred answer in your voice. What do you want this money to do? A kid who has never been asked usually has not thought about it, and thinking about it is the actual skill.

If they want a target, saving toward something specific beats saving in the abstract. Nobody, at any age, is motivated by a balance going up for no reason.

One genuinely good option worth raising once they have real earned income: a custodial Roth IRA. It is the strongest argument for saving that exists at this age, partly because you can offer to match what they put in, which makes it a deal rather than a deduction.

And if they spend it all anyway, that is allowed. The thing to protect is not this particular eighty dollars. It is that the money is theirs, which is what makes the whole exercise real.