Over 300 local students were not allowed at school on Tuesday.
Lambton Public Health Supervisor Erin Courtney says the health unit has not yet received updated immunization records or proof of exemption for 325 elementary and secondary students.
Students will be suspended from school until the necessary records are provided.
In December, approximately 3,200 letters were mailed out to parents of area students whose immunization records were not up to date and a final notice went out last month.
Parents can contact Lambton Public Health via e-mail, fax, phone or in person.
Records include immunizations for diphtheria, tetanus, polio, mumps, rubella, measles, meningitis, whooping cough and chicken pox.
