Low income people already are almost not taxed at all, given how our tax structure works.
The parents that are taxed enough to matter in the first place are making enough money that they can freely give their kids what they want, in general.
EDIT: s/income/sales
That only means at state level and most places will add taxes at a locality level. Consumption taxes in general are popular throughout the world not necessarily because they're optimal or something like that but because they are easiest to enforce and administrate compared to income taxes. Just look at our complex federal tax code for what can degenerate within 60 years. Now, with a VAT things are somewhere in the middle between sales taxes and income taxes and is subject to the same political pressures to shift around taxation toward "less desirable" activities as deemed by politicians.
Oregon (my own state) has no sales tax anywhere, including localities.'
The entire supply chain is taxed throughout, from labour taxes, to service taxes, VAT, property taxes, etc. and all of this ends up in the final price of anything that's purchased. Since the poor usually spend all or most of their income, these things are a much bigger burden for them than for the rich who save most of their income.
Even if you take away the entire supply chain, people are still paying VAT or similar taxes on anything they buy to eat, wear, use, etc.
Poor people don’t have property to have property tax, though.