Those children will have hopefully recovered enough to be aware of their needs and or end up in assisted living.
Who is going to fund assisted living for 20% of the population? Even if the government gave their full support and even if high earners agreed to a 50% tax rate like the many European countries, it's simply not feasible on any level.
Of course, there are going to be exception cases of very bright but anxious kids going on to excel after being taken out the school, but the vast majority of refusers just seem to be idling away their time online. Based on the bell curve, not every school refuser can statistically be outstanding. The majority will be average and compounded with a lack of education, find it even harder to get meaningful work.
It sounds like a ticking time bomb. Even if bunking off was a thing in the 70s-80s, the job market and COL were entirely different. You can do manual work and still support a family. Or buy a house. Businesses were local and people were able to make a living by offering a small service for your community. Now everything has become harder and faster and more competitive at breakneck speed. If you start a shop you can easily be put out of business by cheap shopping apps.
The other extremely worrying factor is that an astronomical number of jobs will be replaced by AI in the next 10-20 years. These are excellent, white collar jobs that require full schooling and university degrees like copywriting, art, design, translation, etc. So even for people who pursued education, there's no guarantee their services will be needed by society.