If your kid is really having a tough time blocking out distractions and staying focused, you might need some technical assistance.
If your kid's school uses a 1-to-1 device program, ask the teacher if it comes with some time-management software or other controls that allow you to restrict access to non-homework-related sites.
Perhaps it's because I'm accustomed to the silence while doing work, but I find that my productivity drops a good 90% while watching TV, 50% with my phone, and 20% with music (lyrics).
Almost everyone has a smartphone these days, and with it comes the ability to rock out to music whenever the mood strikes. Pandora has a comprehensive and frequently updated genre list that you can browse to get started.
Most report that the best studying environment of all is silence.
Since all music processing uses cognitive capacity, the theory goes, listening to music could impair task performance involving your brain.
Here you'll find music suitable for relaxation, spa, ambient, and a whole range of subareas of New Age music types: instrumental, acoustic, solo piano, and beats. The Classical genre has a number of good channels that might trip your studying trigger: classical guitar, symphonies, renaissance, baroque.
A Classical for Studying Radio channel promises a New Age aesthetic and an overall meditative sound. It's quite possible that some people do better with background music: people have different tastes, different study habits, and different ways of handling noise and distraction.
But if your teens' academics are slipping, that's a red flag.
Discuss your concerns and talk about ways to structure homework time, such as turning off cell phones and TV for a certain amount of time or allowing kids to check their texts only after they complete each assignment.