I came into school nursing in mid-spring semester. The old school nurse had basically given up and had allowed kids to just "hang out" and talk, drink juice, etc. The staff had a saying--"If you're looking for your problem students, check the clinic." :angryfire The first 2 months I was seeing 130 kids PER DAY! It took my about a year to retrain the staff and students, and I still had certain teachers sending over 20 kids A WEEK for inane things (chapped lips, torn pants, broken glasses, and the ever popular "female trouble") I really had to come down hard on the staff, going so far as to keep notes on individual teachers and turning them over to the principal. Even so, I could never get my volume under 70/day, no matter what I did. And administration was perfectly fine with that. (That was over 10% of the population every day and I only had 4 students who took daily meds at school.)
A couple things I do--I require that students come to the clinic with a special pass. No pass, no see-um. Unless, of course, they are bleeding,actively vomiting, have suffered a head injury, fainting or not breathing right. There are exceptions to every rule. There is NO "dropping in" to visit the nurse on your way to class. Get a pass and come back. This move eliminated about 40% of my students.
When I spot a trend, I keep notes. If a student has come to me more than 4 times in a 4week period I call the parents about it to make sure there is no unidentified condition(a lot of my parents don't want to let the school know about asthma, diabetes, depression, and ADHD.) Then I lower the boom--I email all their teachers and the principal with my findings, so everyone knows whats going on. I am in middle school, so the kids change classes. They are experts at figuring out which teacher will cave. They will ask each teacher to go to the clinic until they find the soft touch.
I always assess--even frequent flyers get sick. I had one kid, a little fat 6th grader who had pretty severe asthma. His mother had always babied him, picking him up at the drop of a hat. And if she couldn't get there, she'd send one of several aunties. He would come over and over with "difficulty breathing." I always listened to his chest. When I would ask him to take deep breaths he would hold his breath and make whooshing sounds with his mouth. I never said anything, but I would listen for at least 2 minutes. He could only hold his breath about 30 seconds that then he'd take several enormous deep breaths.

Then I'd have him use his inhaler. I found out quickly that he didn't know how to use the inhaler--no wonder his asthma was so severe! Once we got that out of the way and he figured out that I was NOT going to call his mother unless I couldn't get the lungs opened up, he stopped trying to pull that stunt.
Vomiting--if a tree falls in the woods, does it make a sound? If nobody witnesses teh vomiting and they can't manage to vomit in my clinic within 15 minutes they go back to class.
Fever--it has to be over 100. I had one kid who would go into the restroom and gargle with hot water. Too bad that only raised his temp to 99.
One of the biggest problems I have with my school is that over half the students speak Spanish as a first language. The majority of their parents don't speak English and I don't speak enough medical spanish to communicate with them. We have no interpreter so I am forced to let them call parents if there is a question of whether they are sick or not. Of course, they get on the phone and cry and whine and next thing you know here comes Mamacita and Papi.
Finally, teacher education is imperative. I send out a monthly newsletter with short, informational paragraphs about common illnesses. Like how to manage stomach aches in the classroom, how to recognise a real emergency, and when NOT to send a kid to the clinic. I always include some funny anecdotes and questions that come from the kids(and sometimes the parents.) LIke the kid who told me she had been sick all night and still had a bad stomach ache. The cause? "I watched "Saw IV" and I've been ill ever since."

Or the parent who sent her kid to school with a rash and told her to "go to the nurse and see if this is Chicken Pox."

Not chicken pox, impetigo. Pass Go, collect nothing.
I enjoy working with middle school kids for hte most part. I didn't enjoy working for my principal, nor working in the particular school I was in. I never got used to the extreme noise level(screaming, cursing, threatening almost constantly), or the gangs, guns, and violence inside the school. So I quit. I'm now in between jobs and hoping to find something a little less intense.