You’re about to get schooled.

Parents will go wild on back-to-school shopping this year. As the economy and job market improve, the National Retail Federation estimates that back-to-school spending on kids all the way through college will hit $83.6 billion, up 10% from last year. And Deloitte estimates that the average spend will be $1,347 per student.

It doesn’t have to be that expensive. Indeed, many parents are making shopping mistakes that can cost them hundreds of dollars. Here are three:

Mistake 1: You shop too early
Roughly 60% of shoppers hit the stores for their back-to-school shopping before August; they spend an average of $532 on their K-12 kids, according to Deloitte. Meanwhile, those that shop in August or later spend just $458. While all the reasons for that lower spending aren’t clear, experts have their theories. Consumer finance expert Sean Fox, co-president of Freedom Financial Network, notes that parents who shop too early may be missing out on the clearance sales “that usually begin right as school starts.” They may also be missing the sales tax free weekends or days that many states now offer, he adds — most of which are in August.

Also see: 4 mistakes you probably make when you shop on Amazon

What’s more, clothing and accessories are expected to account for 55% of families’ spending – up 10 percentage points from last year, according to Deloitte. But you can cut that down by waiting to buy fall clothes. “Warm-weather clothing is a great deal in August and September when it’s on clearance, while fall apparel is better purchased in October, especially during Columbus Day when sales prices are deepened by extra discounts and coupons,” says Kendal Perez, a savings expert at CouponSherpa.com.

Mistake 2: You avoid the office supply stores
Less than one in three parents plan to shop at office supply stores like OfficeMax, Staples and Office Depot for school supplies, according to the National Retail Federation. That could be a big mistake, notes Perez: “Shoppers assume stores like Staples and Office Depot can’t compete with prices offered by Target, Walmart and even dollar stores. However, back-to-school is the season for office supply stores and they don’t disappoint on the deals.”

In reality, ‘doorbuster’ pricing on basic supplies like pens, pencils, folders and loose-leaf paper can be cheaper than the big-box stores, she explains. (Though, of course, no matter where you shop it’s important to price check and stick to your list.) Office Depot and Office Max, for example, offer “penny deals” on some back-to-school items, which means you can get things like a box of pencils for just one cent (you do, however, have to spend $5 or more on other items to get these deals). And Perez recently found Staples was offering a 10-pack of Crayola Ultra Clean Markers for $3, compared to Walmart’s price of $3.87 for an 8-pack.

Added bonus: “Staples offers a 110% price guarantee which means if you find an identical product priced better at one of their competitors, they’ll match that price and offer you an extra 10% off. It also may be worth signing up for Paribus, which works with a number of office supply retailers; the app will automatically search for price drops at these places and give you the discounts if a price drops.

Mistake 3: You don’t join forces
We all know that buying in bulk at places like Costco and Sam’s can save a ton of money — and yet most Americans — the average family only has about two kids — don’t need bulk buys of school supplies. That’s why you should get together with other parents from your child’s grade to buy supplies in bulk – all the kids have the same supplies list after all, and this can really help parents save.. What’s more, savings expert Ozair Akhtar recommends that you round up parents for an annual swap of clothes and other supplies to save even more. This can be particularly helpful with sporting equipment, which is pricey — and kids often try sports they end up not liking and then you’re just out the money.