Actually, that is rarely true. And often, local public schools send more students on to college than the local charter school that's supported with money the public school would've otherwise had to use.

Some charter schools, roughly half of them, have students who do outperform the local public schools but as you point out, charter schools don't have to keep troublemakers and children who suffer from ADD & ADHD-which are medical, NOT behavioral disorders. Or the poorest children from the poorest families.