You estimated that $300 would cover the tab. But you were $150 shy, and worried.
"I'm doing bad," you said, looking wilted in the sun.
Oh, sweetie. You're miles ahead of kids who've made sickening headlines this summer.
Like the 10-year-old boy who has been charged with beating an older Vietnamese immigrant in her apartment this month. He and a 7-year-old accomplice allegedly used sticks, a rope, a plunger and a plant to assault the woman before stealing $20.
And the two teens, ages 14 and 15, who allegedly raped a 12-year-old girl in the stairwell of a Kingsessing rec center.
And the 15-year-old who was arrested in the July shooting death of a limo driver near Tacony Creek Park.
So, Matthew, you might be short on back-to-school cash. But you're long on character, honor and hustle. Those will take you farther than you can imagine.
"Matthew knows that the economy is really bad and that we're working as hard as we can," says your mom, Maria Laboy, who works in security at Philadelphia International Airport.
Your dad, Junior Marrero, is a laborer who lays blacktop. They helped you scour the house for stuff to sell: a Powerpuff Girls waffle iron, old DVDs and games like Monopoly, checkers and Battleship.
Your parents love flea markets. They find bargain items for you to sell for a profit. The real windfall comes from selling stuff scavenged on trash day. But no matter the profit margin, every penny adds up.
What touches your mom's heart is that you actually understand that.
"He helps with the expenses - he wants to help," she says. "He's respectful. He's not rowdy. He's just a really nice kid."
And your dedication to education is a hit with customers.
Especially clients from ACT II, the methadone clinic around the corner. You have a businessman's appreciation for the ACT II folks, who provide the kind of steady foot traffic that every sidewalk entrepreneur needs to succeed.
Your sales pitch to them?
"Come back with five friends and I'll give you a free movie."
Louis Hernandez likes your moxie.
"A lot of kids ain't doing nothing with themselves these days," says Hernandez, who's at the clinic seven days a week. "It's good to see a kid who works hard."
There's a danger, of course, in being too admiring of a kid who stays out of trouble, since that's the least we should expect of our kids, right?
But the tough truth, Matthew, is that your neighborhood sees more than its share of bad behavior, and children tend to mimic what they see. It can be hard to resist the street, when that's where the action is.
But you're just "not into the drama" that comes with being around trouble. You'd rather stay inside and plan your business moves, so you can spend your own money however you want.
That way, you say, "I never owe anybody."
After eighth grade, you want to attend the Philadelphia Military Academy at Elverson, and then join the National Guard. You'd like to be trained as a medic, someone who is lowered from a helicopter to rescue wounded people.
"I want to be a hero," you say.
Olga DeJesus already has a gig for you. She owns El Cafeito restaurant, on the same block as your table. Behind her restaurant is a shed that she and her brother need to clear out. They plan to hire you to help.
"Matthew has always been a very hardworking young man," DeJesus tells me. A few years ago, she recalls, when you were 11, you ordered lunch and paid for it with cash you'd earned helping a neighbor with chores. You waited quietly for your meal, like a gentleman, and went on your way.
"He's impressive," says DeJesus, who has an old pool table and a sewing machine she plans to donate to your sales effort. She credits your hardworking parents for how well you handle yourself. "They set a good example."
And now you're setting one yourself as you patiently work your table, images of new school supplies pulling you through the lazy end of summer.
Contact Ronnie Polaneczky at email@example.com or 215-854-2217. Follow her on Twitter @RonniePhilly. Read her blog at philly.com/ronnieblog, or for recent columns go to philly.com/Ronnie.