With the critical back-to-school and back-to-college season looming, Target is expanding its offerings for students as well as doubling down on digital experiences and campus events.

The season marks the second-biggest shopping period of the year, accounting for $84 billion in sales and ranking behind only the winter holidays. Between June and August, Target spends about $160 million on measured media, according to Kantar Media.

"We are very excited and optimistic going into the back-to-school season," said Rick Gomez, Target's senior VP-marketing. "Looking at the assortment, it's broader than we've ever had before. …So we're well positioned."

Target says it has added about 200 additional items to its school-themed area in more than half of its U.S. stores, compared to a year ago. In store, there's an emphasis on apparel and matching accessories, as well as fashion-forward school supplies, like glittery calculators and slap-ruler bracelets.

The retailer said it plans to invest heavily in broadcast TV -- it has six ads -- followed by print and radio. There will also be a program with Instagram. Ads focus on celebrating kids' sense of style, a departure from the campaign that has run for the last two years featuring teachers and opening with a salutation to parents. The ads, created by 72andSunny, will air in select markets beginning July 14 and roll out nationwide on July 28.

For back-to-college, there will be a significant presence in digital. "The most important thing we can do is reach millennials where they are, and where they are is the digital space, so we invest quite a bit of our marketing across digital, social and mobile," said Mr. Gomez. "On-campus events are fun, but really the back-to-college marketing cornerstone is digital."

In the digital space, Target will offer online tools to help students create dorm décor and organize lists. The retailer will also host Bullseye University. Conceived out of Deutsch, L.A., it will place five popular YouTube personalities in a dorm, created on a set in Los Angeles, between July 15 and 18. Consumers can shop online for products they spot in the dorm by mousing over the item. They can also interact with the "roommates," as well as participate in online events ranging from music performances to workouts.

Target will also expand its presence on campus with five Live Dorm Rooms, located at Texas A&M, Auburn, Georgia State, George Mason and UCLA. The pop-up spaces will be occupied by a student ambassador and fully furnished with Target products featuring QR codes for online shopping. Target After Hours, a longstanding event that buses freshman to a local store after hours, will also be held at 100 campuses.

"It's a really important season, because if we can get this young adult millennial who is going into a new life stage, it's a way to get a loyal guest for a lifetime," Mr. Gomez said. "We invest a lot to make sure we have the right merchandise. There's a lot of research toward knowing what the millennial customer is looking for."