In our district, all students (new Kindergarteners, returning students, and newly enrolled) are encouraged to have their paperwork completed well in advance of registration night, which is a week before classes begin. They can come into the buildings M-T in June or August and drop it off. The secretary initiates a health file (both electronic and paper) and places it in the nurse's office.
Any newly enrolled student, whether in Kindergarten or a transfer student, must have a physical exam (or signed waiver), vaccine record (or signed waiver), eye exam, which can be completed by an MD, PA or NP during a routine physical (or signed waiver), a student health update, which is a 1-page form comleted by the parents to notify the nurse of any special health considerations such as allergies, asthma, diabetes, seizures, ADD, etc., and also lists immunizations given in the last year, and permission for medications to be administered at school, if applicable.
As for your question about immunization review for returning students: In our district, we fully review immunizations for newly enrolled students. Each year, a list is compiled in every building of students who do not meet immunization requirements, whether due to medical or religious reasons, or non-compliance. That list is reviewed at the beginning of the new school year and updated. Some students will have received shots over the summer, which should be indicated on the health update form mentioned above. Other than the students with known compliance issues, and those whose parents list newly received immunizations on the health update form, we do not completely review every student at he beginning of every year. It' just too time consuming. That said, every time I look up a student's record for any reason during the year, I review immunizations and make certain they are current, as mistakes are sometimes made. So at some point in the year, I look at every student's record and note it as done.
The nurses have access to the buildings (and paid hours) beginning in early August, and are able to complete immunization reviews, establish health plans for students with special considerations, and prepare for medication administration well before registration night and well before school begins. Parents are encouraged to bring a supply of meds to school during the week before classes begin so that there is not a big "rush" on the first day of school.
The immunization reiews and preparation for students with daily meds and special health needs are non-negotiable and must be completed prior to day 1. Review of physical exams, eye exams and minor health considerations are less pressing and can be accomplished in the first week or two after school starts.