The residency checks, conducted on a daily basis by a full-time administrator, are intended to uncover students who do not legitimately live in the district. By removing these students from enrollment the district estimates it saves about $2 million each school year.

"Each student costs the district between $6,500 and $8,000 to educate for the year. Catching 100 people, well, do the math," said John Lozano, the district's student welfare and residency administrator.

Fremont Union's option of receiving "basic aid" means it does not receive money from the state on a per-pupil basis, as do other districts. Instead, the district's main revenue source is property taxes, including a $100-per-parcel tax passed in November 2004. The tax base in communities with high property values mixed with a good commercial business base provide more money to the district than if it opted for the average daily student attendance revenue.

In order to keep providing the same level of education service to students and the community, district officials believe they need to crack down on residency cheaters.

"Our promise to our taxpayers is to be diligent," said Shelby Spain, the district's director of attendance, guidance and alternative programs.

Residency checks such as this will not be a once or twice a year practice. It's not going away.

"When do we stop? I don't think we're going to," Lozano said. "We'll be as diligent if not more so in the coming years because we realize the district has to do this to maintain a strong financial base."

That robust fiscal base is what drives the education engine, Lozano said. The good schools in the area draw home-purchasing parents to the area. Typically, those parents value education and are well educated themselves. They can afford higher home prices, thereby driving up housing costs. In turn, they want the schools to maintain their academic prowess.

So driven are some parents to have their children attend Fremont Union's schools that Lozano has come across non-district parents who have paid residents anywhere from $500 to $1,200 a month to use a false district address.

He said he once found a four-bedroom house in Cupertino owned by a "fairly young couple" who were sharing one bedroom with their young child and renting out the other three rooms for $2,000 per month to parents who had children they wanted to attend the district's schools. One room was occupied by a 16-year-old boy and his 12-year-old sister, he said.

Since July, Lozano said he and his staff have conducted residency checks on about 500 students, netting about 20 percent who needed further verification.

That verification has resulted in finding some students who no longer attend district schools, while others are able to prove residency. Others received letters before the school year began, instructing parents to bring in documentation or get their children enrolled in the district in which they belong.

"We sent out letters to over 80 kids and then dwindled it down," Spain said.

They were given until Sept. 30 to come up with the proper documentation, which includes such items as tax returns, property tax bills, lease agreements and photo identifications.

About 40 of those students were asked to leave the district because they and their parents or guardians were unable to prove residency.

When the program first began, the district received criticism for kicking students out in the middle of the school year. But Spain and Lozano said they are trying to be sensitive to students' needs and transition periods and work hard to time "disenrollment" with neighboring districts' schedules, where the students actually belong. Lozano also said that although the Sept. 30 deadline fell shortly after the school year began, the date was selected to allow parents as much time as possible to come up with proof of residency without disrupting the student's continuity of instruction.

Another big push for residency verification will begin in January or February, Spain said. So she wants parents to be prepared.

Most parents who have been contacted to verify residency have been grateful that the district is following up, Spain and Lozano both said. Even those who are caught cheating, for the most part, have been obliging.

"Most just say, 'Yes, it's true,' and just go ahead and disenroll. I'm surprised at how compliant they are," Spain said.