not all school districts screen for drug use most wont test for steroids because they cost a 100$ per test alot do test for weed if you smoked last week and you go next week you will be cutting it close thc generaly stays in your system for 30 days coke and heroin 2-4 days benzo's [ valium / xanax ect.] a few weeks lsd no test will detect if your worried id go with the kidney flushing tea several brands aval try high times or pot tv news or cannibis culture magizine for types and costs or your local neighbor hood head shop good luck and let us all know how it works out for ya