Shouldn't charter schools outperform public schools based on the fact that they have parents and children that are specifically seeking an excellent education? Especially in situations where students are chosen by lottery.
As a public educator, in a socio-economically diverse school district, I typically find one or two students in each of my middle school classes that has chronic attendance problems. We contact the parents, connect the student with counseling, make outreach programs available. Regardless of attendance, we work to educate the students as best we can.
I would expect that charter schools, having only dedicated students attend, ought to have better results than public schools hands down, but this isn't the case.