The Linden Store has known about it for years. In fact, owners have alerted other businesses in the two squares, Linden and Wellesley, to prepare for the onslaught.

If it's the first Wednesday of the month, it's a half day at the public schools. And that means large groups of tweens from the middle school and teens from the high school spending time and money and increasing foot traffic considerably. The next half-day is tomorrow, Dec. 7.

And what do students enjoy? Eating out mostly, so it is not uncommon to see long lines at Starbucks, Peet's Coffee, Bruegger's and The Linden Store when schools let out at about 11:30 a.m.

Most parents will tell you that allowing 11 and 12 year olds to be out and about is a right of passage in Wellesley. Students have been doing it for decades, and the lunchtime visits from students have become a tradition.

Most businesses seem to welcome students, with only a few exceptions.

The Linden Store, Wellesley's go-to sandwich shop, welcomes a ton of middle and high schoolers on the monthly half-day. Employee Natalia Escallon says the large groups of students can get excited and also very loud during their visits, but she says the half-days "offer a great opportunity for kids to be on their own in town, learn a bit about managing money by making their own transactions."  

She says that some parents of sixth graders often call ahead to place an order at the Linden Store, especially when going out with a large group after school is new.

At Linden, half-day lunchers "know the drill," and wait patiently in line to order their favorite sandwich or sub.

For the past two decades, the Linden Store has offered a special treat to the first middle-schooler to arrive for lunch on each half-day of the school year: a FREE sub. And Linden's regular non-student customers also seem to oblige the extra crowds and noise, because they too, have become accustomed to the monthly half-day "organized chaos."

At the CVS on Central Street, extra staff is part of the plan to handle the crush of youngsters who want to spend time shopping and buying in the midday hours. The store requests that students leave their backpacks at the door, which is why one can often see them piled up on the sidewalk.

Over at the CVS on Linden, which is closer to the middle and high schools, students are also asked to leave backpacks at the door. One employee at CVS tells me that the store generally has a full cashier staff on half days to try to accommodate the crowds. In addition, a staff person is at the door, allowing young shoppers inside in small groups, so that all shoppers inside can be waited on.

At California Pizza Kitchen in Linden Square, manager Dan Garden says he first learned about the pick up in business from the also-popular Linden Store, where the lines on the half days can stretch out the door. Garden says for the most part, youngsters are good about tipping their servers, and that's another way our students are learning about commerce and how to reward good service.  

The restaurant automatically adds a gratuity for parties of eight or more. While the dining room is large enough for 175 diners, Garden says California Pizza Kitchen tries to separate the young diners from the business-lunch crowd of regulars.

Truly Yogurt and Pinkberry see big crowds the first Wednesday of each month during the school year. Merchants say our children are respectful and prepared for their "commercial transactions" they carry out, and do not complain about long lines and rules about backpacks in the stores.

Wellesley Police Lt. Marie Cleary says a liaison for her department has worked with the middle school on issues relating to the half days. Cleary says if "half-day" issues come up with retailers, more education at the schools about how local businesses are affected is communicated. Cleary says the school and students are receptive.

Parents, do you use the half-day as a "teachable moment?" And retailers, what does your business do to accommodate the extra crowds on the half-days?