Look at it this way. I’m a high earner. High taxes mean less money in my pocket, which means I am worse off in terms of my household budget.
I am also someone who uses public services. Higher taxes means the public services that I use are better.
So should I vote for the party offering tax cuts and austerity, or the party offering increased public spending and a higher band tax increase?
The answer is, what is more important to me? What choice do I make? Which priority is more important to me - more money in my pocket, or better public services?
No independent body could ever make that decision for me. Only I can make the decision about what I value more.
That’s why nobody can cast a vote for children on the basis of what is ‘objectively’ best for them. Voting is always subjective.
I would say for certain children there are poilicies that could pretty objectively be deemed to harm that child's interests. I am thinking of some of the welfare reforms that have disproportionately affected some families and have led to some pretty dire situations.
Welfare reforms might disproportionately harm children, but they might benefit others (perhaps those whose parents have more money due to tax cuts).
Children don’t have identical interests by virtue of their being children. And their interests cannot be objectively measured.