These families may not mean any harm, but suburban districts say their dishonesty has put a financial strain not only on them, but also on the taxpayers who end up footing the bill.
With more school districts feeling a financial squeeze, fiercely protective school officials have gotten tougher with getting rid of outsiders.
More of them have removed students from schools, fined parents and forced them to pay back tuition, earning them the ire of school-choice advocates who say the parents are only seeking better opportunities for their children.
James Wigo, assistant superintendent for curriculum and instruction for the Upper Darby School District, has seen hundreds of cases of illegal students.
"School choice can't be a free-for-all," he said. "It's a tremendous burden on the taxpayer and the district." He said the problem in Upper Darby has gotten so bad over the past several years that officials reinstituted a screening process to keep track of students' residency.
And when the district suspects foul play, private investigators are hired to follow students and their families.
Illegal registration has cost the district millions and puts it at risk of getting audited by the state Department of Education, which monitors students' residency, he said.
"When I say it's a major problem, that's a relative term," he said. "We have no way to plan what we would need because the numbers are always shifting. It's like punching a butterfly."
Safer schools, better academic programs, scholarship opportunities and college access are major reasons why Philadelphia parents enroll their children in other districts, said Gerald Wright, co-founder of Parents United for Public Education.