The Pacific Collegiate School in Santa Cruz, Calif., is a public charter school. It must hold a random lottery when it has more applicants than vacancies. It is not supposed to be selective.

Yet somehow its average SAT score has risen to the top tenth of one percent among all public schools nationally. Less than ten percent of its students are low-income, compared to 40 percent in its city. Maybe that has something to do with the fact that the school is allowed to ask (not require, its principal emphasizes) that every family donate $3,000 and 40 hours of volunteer time a year.

As a supporter of the charter school movement, I get grief from people who say that charters—independent public schools using tax dollars—are private schools in disguise. They are almost always wrong about that, but there are enough Pacific Collegiate situations to make me wonder if the rules need revision.

Places like California, where the law allows some preferences, are more likely to have this problem than D.C. The District’s charter law and demographics would give Pacific Collegiate a much more diverse student body.

That still leaves selective practices like the seven-page form, including essay questions, that applicants must fill out for the Gateway High School charter in San Francisco, or the lottery-exempt status as “founding parents” offered by some Los Angeles charters to applicants who promise money and volunteer time, as revealed by the L.A. Weekly newspaper.

Todd Ziebarth, vice president for state advocacy and support at the National Alliance for Public Charter Schools, said vague state laws let charter authorizers, such as universities, state or local school boards, occasionally wink at loopholes. To stop that, 12 Newark, N.J., charters have signed a compact barring any burdensome requirements, like attending information meetings or filling out long forms, before their lotteries.

There is a subtler issue. What if parents and students are discouraged by the higher standards that make the best charters worth attending? The KIPP schools, part of a charter network with longer hours and proven achievement gains, require that students, parents and teachers sign contracts affirming their responsibilities, such as promptness and good behavior. Some readers have told me they assume that students who violate those rules are expelled. The truth is that such contracts have been used by teachers to set guidelines in regular schools since long before KIPP began. Violators may be mildly disciplined, but not expelled.

I know that because I have investigated KIPP for ten years and have written a book about it. Some parents don’t have the time or inclination to ask a lot of questions. I can see why they might get the wrong impression or might just think their child is not up to so much work.

Pacific Collegiate principal Archie Douglas reminded me that his school requires every student to take at least five Advanced Placement courses. I think that’s great, but not all parents agree with me. Douglas says his school’s request for funds and time is necessary because California financial support for charters is so low, about half of what D.C. charters get. Only 30 percent of his families donate as much as $3,000, he said, although he was surprised to learn that a page on the school Web site still said the 40 hours of volunteer work was mandatory. He said he would have that statement deleted.

His school’s distance from large low-income neighborhoods frustrates recruiting, but last year the school reserved six of a possible 56 slots for a lottery just for students whose parents had less than two years of college.

Gateway executive director Sharon Olken defends her application essay questions as a way to help parents and students think through what kind of school they want. Their answers are not read until after they are admitted. Nearly half of Gateway students are low-income, close to the city average, despite the long form.

I still don’t think they need the essay questions. Charters spend public money. They should do everything possible to convince parents their doors are open to all, as long as that doesn’t get in the way of the deep and imaginative teaching that they are there to provide.