A study into American online charter schools has shown that they are rubbish, and in the case of maths, the student might as well have not attended school at all.
www.washingtonpost.com/news/answer-sheet/wp/2015/10/31/study-on-online-charter-schools-it-is-literally-as-if-the-kid-did-not-go-to-school-for-an-entire-year/?postshare=8681446659837080
It's worth mentioning that they are not the same as UK online schools and students get far less contact time with teachers.
But it is interesting to note that you can't stick a kid in front of a computer and expect them to teach themselves. That will be a bit of a blow to the government, who I'm sure would be glad to get rid of the need for pesky teachers in front of classes.