Parents can already deregister their children and home educate them if they so wish. No petition needed
If you are suggesting parents should be allowed to keep their child at home indefinitely while their school place sits empty then that is a different matter entirely. The problem with this is that it's difficult to plan staffing, to plan places for pupils who move into the area and need a school place. Also, the expectations on schools/teachers. Are they to be expected to provide full time education in school plus simultaneously provide home learning for those at home and still be responsible for monitoring their progress and ultimately be responsible for their exam results? What about parents who don't get their child a place at their preferred school but that school has places not being used -how long should that be allowed to go on for.
Ultimately, it is a parents right not to have their child educated in a school setting but the alternative is deregister and home educate. Obviously, this does not apply where a child has an illness/disability which means they are unable to attend for long periods of time.