Unexpected back-to-school expenses can easily add up this fall

Watch out, parents: Back-to-school season can easily put a four-figure dent in your budget.

Parents of high school students can expect to pay an average $1,489 per child for school supplies and activity fees, according to the annual Huntington Bank Backpack Index. That's a drop of $9, or less than 1 percent, from 2016.

Parents of elementary-school students can expect to pay an average $662 per child, up 1 percent from last year. Middle-school students' parents will fork over $1,001, a 4.6 percent increase.

Some parents expect to shell out even more. One in 5 parents said they plan to spend more than $2,000 per child in back-to-school shopping, according to a new Capital One survey.

Teen boys and girls said the most important items to have when returning to school are new clothes and new shoes, according to Ebates Back to School survey. But other expenses aren't ones parents or kids might expect. The Huntington Backpack Index cites under-the-radar purchases such as tissues and dry-erase markers for the classroom, and a graphing calculator for older students.

Here are some of the other big-ticket back-to-school purchases to watch out for:

Many students enjoy playing for their school team. They get a chance to wear their school's colors, practice their skills and bond with teammates.

That privilege can be a pricey one, however, especially for students in middle and high school. The Huntington Backpack Index estimates sports participation fees at $150 for middle-school students and $375 for high-schoolers.

If your student has designs on college, those expenses can add up.

The Huntington Backpack Index cites $235 in college prep expenses, including study books for the ACT/SAT and AP exams, and fees for taking those exams. Expect higher costs if your student takes the SAT exam more than once, or takes multiple AP classes.

College prep expenses are down from $291 last year, largely because of a 61 percent decrease in the cost of prep books for the ACT/SAT, according to the survey's price charts.

School expenses don't stop after the academic year begins.

In the Capital One survey, 40 percent of parents of elementary-school students cited school pictures as their biggest expense during the school year. Yearbooks are another pain point, especially for parents of middle- and high-school students (29 percent).

Parents expect to spend an average $204 on electronics as part of their back-to-school shopping, according to the National Retail Foundation. Among the 60 percent of parents who said they would be shopping for electronics, 45 percent said they plan to buy a laptop computer and 35 percent a tablet.

Even elementary-school students may not be tech-free: The Huntington Backpack Index includes headphones on the supply list for those students (but not middle- or high-schoolers). That's an extra $10 on parents' tab, down from $15 a year ago.