SPOKANE, Wash. (AP) -- Spokane school district officials on Monday removed from class 143 students who could not prove they had legally required vaccinations. More than 700 students in the state's second-largest district lack complete vaccination documents, so that number was expected to rise, district spokesman Kevin Morrison said. The crackdown began Monday morning. The Spokane district was believed to be the first in the state to take this action, Morrison said. "We're the front-runners," he said. "Given the increased awareness that the world has of the possibility of pandemic, I think heightened awareness is certainly not a bad thing." Students who are removed from school can return once their parents either get the required vaccinations, or sign waivers saying they were opposed to one or more vaccinations, Morrison said. The Spokane district has about 30,000 students, and only about 729 students lack the required documentation, he said. The recent measles outbreak across the nation pushed the district to review its vaccine compliance rate, Morrison said. What they discovered led them to change their process and insist on documentation for every child. He could not speculate on whether other school districts in the region or the state would follow. After the measles outbreak, Spokane district officials discovered about 6 percent of their students lacked proper vaccination documentation. In February they launched a program to inform parents that their children needed vaccinations or waivers. The school district and the Spokane Regional Health District also held a series of vaccination clinics. That helped drop the out-of-compliance rate to about 3 percent, Morrison said. Ensuring students are vaccinated is complicated because 60 different languages are spoken by students in the Spokane district, and about 30 percent of the students leave their school each year, he said. Tracking vaccinations is especially difficult for students who come from out-of-state or other countries, he said. Complete documentation is important to protecting students, Morrison said. For instance, if there were a measles outbreak in a school, officials would like to know which students have not been vaccinated against the disease so they can be sent home, he said.