When I was at the high school yesterday for a Board meeting, I literally ran into one of the seniors when she plowed into my back, her nose in her cell phone, madly texting.

I should have known better than to think she was merely chatting with a friend, even though she was late for class. This senior is one of those enterprising ones, the sort who makes me remember my incredibly lazy high school days with embarrassment.

“Do you use an online travel agent?” she asked.

First of all, I can’t remember the last time I could afford to go anywhere. Second, what’s an online travel agent?

“I’ve used Expedia,” I said.

She wasn’t impressed. She was trying to comparison shop airline tickets to have her favorite aunt come for Thanksgiving, an aunt who said she couldn’t afford to fly across the country from California to New York this year.

“Even Travelocity is better than Expedia. We’re still more than 30 days out, best price so far is $267 if she leaves the Saturday before. I’ll ask for donations from every family member. Can’t be that much each. I have a big family.”

She ran off to Calculus and I stood there, thoroughly impressed by her planning skills and strategy. And, of course, it then occurred to me to turn this one-month-in-advance sweet spot in time into a money lesson for teens that aren’t so enterprising without a little nudge.

What all teens are good at is online comparison shopping, if you put it to them the correct way, as in: Pretend you’re buying something for yourself, and you desperately want it, but have a limited budget. They instantly become Google Jedis.

So, here’s the holiday money lesson to hand your teenagers this weekend, while there’s still 30 days before Thanksgiving. It may save you a bundle, while showing them how expensive holidays can be:

1. If your family is traveling somewhere, have them do a cost analysis of the trip, by creating a ledger of line item expenses. Before you tell them which line items to include, see what they come up with on their own. It’s interesting to see which expenses they’re aware of, and which ones don’t come across their radar.

Ultimately, the line items for travel should include Travel, Lodging, Daily Expenses.

First, will there be air travel for the family (or cost of car travel). Air travel means asking if there are frequent flier miles available for any or all of the family, and then seeing if they’re worth using, or if the flights are cheap enough that the miles should be saved for another time. It also means comparing flight routes and possible days of departure.

Car travel means calculating gas and parking costs. Maybe train travel is another option. Have them look into all transportation options.

Then they should include whether the family is staying at a relative’s house, or at a hotel. If a hotel, have them comparison shop hotel prices online. Also include rental car, parking, and gas costs if they apply.

2. If you are staying home this Thanksgiving, let your teens do the grocery shopping, and any other related expenses. If your family is entertaining this Thanksgiving, expenses add up quickly.

First of all, you buy a lot more food and possibly wine. If you host guests, there may be outings that are costly. Have your teen create a ledger of line item expenses for all these costs.

The ledger should include: Consulting about the size of the turkey (or whatever your traditions are) and then comparison shopping the best place to get what you’re looking for. Many people order turkeys now or pretty soon. Then: other food, comparison shopping the price of any wine or beer online or on the phone (naturally you can’t send them out to get these items). I include the liquor not to invite aghast emails, but because it’s a considerable expense that we end up paying. Then other expenses, such as an ice skating or movie outings for the extended family.

When it comes to activities, have the teens brainstorm what would be fun and at what cost.

If it’s possible, compare what costs your teens come up with to what you spent last year. Really go to some effort to look up last year because it will be very satisfying to the kids to know.

I’m curious if they save you money. My bet is they will, simply by creating awareness early and then planning. We’re all so busy we tend to shop last minute (I’m the absolute worst when it comes to that). Last minute shopping is always expensive. To have everything mapped out in advance is a great lesson in planning, too. Maybe it will spill over onto their schoolwork. Hey, I can dream, can’t I?

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