I admit, our tv is almost always on. Both boys have learned extensively from the tv shows (mainly PBS and some shows on Netflix and Amazon Prime). Neither my husband or I are native English speakers and DS4's English is PERFECT! I'm pretty sure his Aspergerish traits play a bit of a role in it. For us TV is our kids English class. And they are the kind of kids who don't just sit there and stare ... they really absorb the info. The older one likes the TV on while he's playing and the younger one likes it quiet when he's playing so it's always a little fight over TV in our house but overall, I watch it, they watch it ... and when for couple weeks we tried to minimize TV to about 60 minutes a day, I didn't see any difference in their behavior so we just go with whatever seems right that day.