When school starts in a few weeks, a chosen few will triumphantly enter Silicon Valley's top-ranked schools.

And then they'll start kindergarten.

Some of California's highest-achieving public schools have a policy of ``open enrollment,'' which ostensibly welcomes students from all across each district. But as unwary parents in Santa Clara and Cupertino are finding out, it can be extremely difficult to get their children in.

That's because a huge share of kindergarten spots at the most coveted schools go to siblings of students already enrolled. The rest have to take their chances in a lottery.

In some cases, those chances aren't so good. At Santa Clara Unified's Millikin Elementary, one of two schools in the state with perfect standardized test scores, only 4 percent of the spots for this fall went to kids in the lottery.

Predictably, this system leads to some high-level frustration among parents who have one child. When Kate Grant lost out on the lottery to enroll her son this year in another open-enrollment school, Washington Elementary in Santa Clara, she decided to yank him out of the district entirely, and put him into private school.

Santa Clara Unified also gives preference to children of district employees. So Grant's chances of winning one of the remaining kindergarten spots in Washington's lottery were only about 30 percent.

``They're supposed to be a public resource,'' Grant said of the open-enrollment schools. ``I think this is scandalous.''

District officials are quick to defend the sibling policy. ``It's a pain for parents'' to have children in different elementary schools," said Roger Barnes, spokesman for Santa Clara Unified School District. There would be two sets of open houses to attend, two sets of parent organizations to join, and -- maybe worst of all -- two transportation routes to deal with.

``From a parent's standpoint,'' he said, ``it doesn't make any sense to force them to have kids in two different schools.''

But to parent Jay Keehan, it makes no sense that the schools claim to have open enrollment.

``What I resent is, I went through the bother of visiting Millikin, when my son had almost no chance of getting in,'' he said. ``I don't think people have any idea how dismal the chances are.''

Keehan ended up ``not even trying'' the Millikin lottery. He did try Washington, but didn't get in. So he, like Grant, chose to enroll his son in private school rather than send him to a lower-performing school in the same district.

``My wife and I can afford a private school, because we have only one kid,'' Keehan said. ``But I realize for some people the stakes are a lot higher.''

Most district officials will tell you a student can get a good education in any of their schools. Although that is somewhat disingenuous -- because school quality usually varies according to the socioeconomic status of students -- it is true that most schools within a district offer a uniform curriculum.

Open-enrollment schools, sometimes called magnets, can be different. They might offer a specialized curriculum, such as Hacienda in San Jose, which specializes in science. Other schools stress a no-nonsense, back-to-basics approach, concentrating on language and math. That specialization helped Millikin and Cupertino Union School District's Faria Elementary last year become the first schools in the state to record perfect 1,000 scores on the state's Academic Performance Index Growth Report.

Although the demand for spots in those schools is great, Barnes says it's not enough to open another school. So, hopeful parents in his district are stuck with the lottery. (That's not the case in San Jose Unified, where kids can enroll in schools outside of their neighborhood based on their socioeconomic status. The policy resulted from the district's lengthy desegregation court battle.)

Grant says she protested Santa Clara Unified's policies all the way up to the superintendent, before giving up and enrolling her son in private school. She admits she doesn't have a perfect solution. ``The individual policies are not bad,'' she said of the selection criteria. ``But the unintended impact is discrimination'' against parents with one child.

Barnes admits there is no perfect solution. Told of Grant's remark, he admitted, ``She's got a point.''