All jokes about “new math” aside — have you tried to help your kids with their homework lately? A growing number of online, on-demand tutoring services might just be your saving grace.

The K–12 online tutoring market will grow to nearly $121 billion by 2021 from around $64 billion in 2016, according to market researcher Technavio. One of the biggest reasons? The on-demand aspect tackles an immediate need, in a way that resonates with today’s tech-savvy students.

Practicing French with a Varsity Tutor.

While the "old-fashioned" practice of hiring a tutor to come to your house, or going to a tutoring center, still works just fine for some people, technology makes it easier and more efficient than ever to have an entire tutoring session over video chat or via direct message.    

My own teen uses a site called Varsity Tutors for AP French. In order to pass the Advanced Placement test, she has to practice speaking French at home. We can’t help her with that.

Instead, she logs into the site and requests a tutor in “Conversational French.” As soon as she does that, a window opens that prompts her to describe her goal for the session. Within a few minutes, she’s connected to a professional tutor. She can do this pretty much any time, day or night, even on the weekends.

So far, all of her sessions, in her words, “have been awesome.” She’s had three different tutors and, though she has a favorite, she says all have been equally helpful. The convenience of doing this kind of tutoring wherever she is, and whenever it fits into her schedule, works really well for our busy family, too. And every tutoring session is recorded so that students can review and practice what they learned.

For this, we pay around $62 an hour, with price breaks for buying a package of minutes. The sessions can last as little as 15 minutes, or as long as a few hours, depending on what students need and what the tutors have time for.

Yes, it’s expensive. Where we live in Northern California, everything is expensive, and the average price of a deeply vetted in-home tutor is $90-$100. I keep thinking that this extra expense is worth it if that means it satisfies a college requirement, which could easily cost thousands of dollars more.

The company picks tutors based on a number of criteria including background checks, reviews of past transcripts and standardized test scores, a history of tutoring or teaching, and in-person and video interviews to “determine friendliness, communication, ability to develop learning plans and how effective they'd be as a tutor.”

Tutor offered up a shared screen and direct messaging with a tutor named Zainab A.

There are several other companies that offer similar services. We also tried Tutor.com, which acquired well-known test prep company, The Princeton Review, a few years ago, Chegg Tutors, and Mindspree. We went to all three of them with the same task: Read through my daughter’s Honors English 3 essay, and suggest ways she can make it better. Of the three, Tutor.com was the fastest and least expensive (she only used the free 30 minute introductory offer for the review), but Chegg was the most helpful (and it also offered a free 30-minute trial).

Mindspree lets you request a tutor and name your price. We offered $30 for the project, since the others were less expensive than that, and we kept checking back for about 12 hours. No one responded to our request for help, so we gave up on that one.

After giving my name and credit card billing information to Tutor  it offered up a shared screen and direct messaging with a tutor named Zainab A. She dove right in, read the essay and suggested that my daughter add a bit of context to one portion. After that, she went through punctuation, asking about comma placement. She asked the question of whether the comma looked like it was in the right place, versus just telling her to the make the change, which was a helpful teaching aid.

At the end of the session, you can rewatch it or print it out. Tutor.com offers packages for monthly tutoring minutes, starting at $40 for an hour on up to $240 (40 cents per minute) for 10 hours of tutoring per month — with any time you don’t use rolling over to the next month.

Chegg has a deep tutoring base mainly for high school and college aged students

Chegg has a deep tutoring base mainly for high school and college aged students. It works basically the same way as Tutor, but the site is even easier and more user-friendly overall. Just download the app or sign up online, type in your question or summarize what you’re looking for help with, and within minutes you are texting with a tutor. Chegg also gives you the option to do an immediate online video chat and share a screen to work through problems together. We chose “written only,” for this one and asked for a read-through of my daughter’s English essay to be completed and returned within a four-hour time frame. The tutor, identified as Martha Z., had it back within an hour.

Her remarks were the most insightful and helpful of all, which was no surprise given that her Chegg profile showed that she has a Doctorate in Education, and two Masters. Comments like, “add content with a modern-day parallel,” or “You have a strong topic sentence here. I have shown you how to transition to get this into paragraph form,” were just the kinds of notes my daughter needs to go from good to great.

The price for this service? We requested an hour with the tutor and the first 30-minutes were free, so we ended up paying $22.50. The site also has discounts if you buy a package, such as four hours of tutoring for $196 per month (about 40 cents a minute).

As a family, we’ve long used Kahn Academy, which is free, and also offers thousands of practice exercises, instructional videos, and a personalized learning dashboard to help students of all ages. Like many of the paid services, it’s a great resource not only for classroom help, but SAT and other college prep and now even offers help with college admissions too.

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Jennifer Jolly is an Emmy Award-winning consumer tech contributor and host of USA TODAY's digital video show TECH NOW. Follow her on Twitter @JenniferJolly.