Why do school districts do routine checks for lice, scoliosis, etc, but never for STIs?

As far as things like lice, they need to control things that can be transmitted on their watch. A lice outbreak may just be a nuisance, but it is difficult to contain once it spreads to a large percentage of the student population. They check for scoliosis because things such as carrying heavy book bags and participating in physical education could contribute to the problems. STIs aren't something that should be spread at school. It's on a very rare occasion that students will be engaging in sexual activities during school hours. On top of that, many ignorant parents have enough of a problem with sexual education courses, and encouragement of safe sex. If their children were required to submit to tests for sexually transmitted infections, the school district would have some very angry lunatics on their hands. As helpful as school mandated testing may be, I don't see it happening in the near future.

The testing for STI is invasive. Lice and scoliosis can be checked by observation. No lab work needed.

In Middle school? That's when they check for scoliosis. That's too young for adults to handle, to think kids are having sex that young.

School nurses aren't sophisticated enough to screen for STDs, and aren't going to pay medical professionals to come in when you can go to a clinic for free.

Schools are not medical centers.