Tens of thousands of school children across the Chicago area may not be vaccinated for a variety of serious diseases, posing a potential health risk to their immunized classmates, NBC 5 Investigates has found.



What's more, hundreds of public and private schools in Chicago and suburbs have high levels of students with no records of vaccinations - sometimes more than a third of the students in a single school. And hundreds of other schools have not reported any vaccination information to the state in years - even though it's required, annually, by law.



Any parent with a school-aged child knows the drill -- submit proof at the beginning of the school year that your child is up-to-date on immunizations, or risk a stern letter or repeated phone calls from the school until you finally submit the records.



At least that's the way it's supposed to work. Illinois school children are required to be vaccinated for a variety of dangerous diseases ranging from measles and mumps to diphtheria, pertussis, and chicken pox. Although some national organizations continue to insist that immunizations can be harmful, the science is settled: Vaccines are considered safe, and - as a rule - about 90 to 95 percent effective.

But it's that slight chance of ineffectiveness that can put immunized students at risk if they're sitting in classrooms with children who are unprotected from disease. Recent outbreaks of measles in New York and Los Angeles - along with a 2012 outbreak of whooping cough in the Chicago suburbs - prove that no one is completely safe from these diseases. So -- by law -- a school can refuse to admit any student whose immunization records are not on file. Those parents who insist on not vaccinating their children must provide a valid and approved letter of exemption, explaining why they can't get immunizations - for either medical or religious reasons.



Everyone else needs to get up-to-date on their shots.

But NBC 5 Investigates found 369 public and private schools across the Chicago area where more than 10 percent - and as many as 76 percent -- of students are not vaccinated for one or more serious illnesses. That's more than one in 10 local schools where the rate of unprotected kids exceeds state and national maximum standards.



An additional 638 local schools didn't submit their most recent information to the state - an apparent violation of state law. And most of those schools - 538 total - have not submitted the required information for the past five years in a row. That's more than one in every seven Chicago-area public and private school where parents are supposed to be able to get information about immunization rates, but can't - because the school doesn't follow the law in supplying the numbers.



But NBC 5 also found that there's little - if any - enforcement on the state or local level, either for those schools reporting high rates of non-immunized kids -- or for those schools that don't bother to report at all.



"We mostly try to work with them to get them in compliance," said Mary Fergus, spokesman for the Illinois State Board of Education. She pointed out that on the district level, ninety-seven percent of Illinois' public school districts are officially in compliance - meaning they report fewer than 10 percent non-immunized students district-wide. Fergus said it's up to each district to make sure its individual schools are complying.



But for those schools that don't comply, the Illinois School Code states that the ISBE can temporarily withhold funding from any public school district with more than 10 percent of non-immunized kids, until the school gets in compliance. However, Fergus admits that's never been done.



There appears to be even less oversight for Illinois' private schools - even though they're subject to the same rules as public schools in keeping non-immunized children to less than 10 percent.



That's what Debra Benson found when she took over six months ago as superintendent of Park View Christian Academy in Yorkville. State records show that more than three-quarters of Park View's students did not submit immunization records for the 2012-2013 school year - the second year in a row that the school's immunization rates did not meet state and local standards.



Benson said there was little emphasis on vaccination compliance when she took over at Park View, and that she has spent a lot of time getting parents to understand the importance of these shots - and the need to submit records.



"I don't really know who has an exemption and who doesn't - who's immunized and who isn't," she said. "And [if] someone comes to school with meningitis tomorrow or some other disease, how can I protect anybody? Because I don't know for sure."



Even as Benson tried to follow up, it doesn't appear that the state does the same. The ISBE's Fergus admits no one on the state level checks - beyond the yearly reports - to see if the non-immunized students eventually got their shots, submitted proof of immunizations, and possibly lowered their school's rate of non-vaccinated children. She suggested that parents should contact a school directly for that information.



You can search for your school's information on our database, or go to the Illinois State Board of Education's web site for data analysis and accountability, and look at the Immunization School Survey Results for each year.