In establishing the right to a free public education, the Missouri Constitution deems knowledge “essential to the preservation of the rights and liberties of the people.”

This high-minded language is as relevant and important today as it was when this document was adopted. However, we’ve learned over the years that free doesn’t mean completely free, even in the public schools.

There are always fees and add-on costs. For 13 years, Huntington Bank has tracked the out-of-pocket cost of school supplies to highlight the impact of education expenses, especially on low-income students at the start of the academic year.

This “Backpack Index” found that a typical U.S. family needs to fork over more than $1,000 per student for school supplies, technology and extracurricular fees. For elementary school students, that’s a 59 percent increase in one year. College-prep materials pushed the average cost for a high school student to more than $1,600, according to the survey.

In a town like St. Joseph, with around 70 percent of students qualifying for a free or reduced lunch, that kind of expense makes a difference at a time when computers and electronic devices are an important element of a child’s education. To help ease this burden, St. Joseph residents are fortunate that this city participates in the annual sales-tax holiday weekend for school-related purchases.

This tax-free weekend also benefits teachers, who spend an average of $500 of their own money on school supplies every year, according to the same Huntington Bank study. Some might think that number sounds low.

Beginning today and running through Sunday, customers pay no state and local sales tax in St. Joseph on back-to-school purchases, including clothing, school supplies and computers. That’s a savings of more than $8 on a $100 purchase. It might not sound like much, but it adds up on larger purchases.

In cities that don’t participate, like Savannah and Chillicothe in Northwest Missouri, shoppers pay the local tax while the 4.225 percent state rate is waived. Statewide, Columbia, Jefferson City, Springfield and several St. Louis suburbs are among the largest cities that opt out.

Also this weekend, the tax break can be applied to qualifying items purchased over the internet, according to the Missouri Department of Revenue, but we encourage St. Joseph families to shop in local stores and take advantage of this program.

Consider it your first lesson of the upcoming school year. The importance of an education won’t diminish and the out-of-pocket cost is unlikely to decline.

Parents can do the math and figure out the value.