In order to qualify for a license, a gym teacher must have a minimum of a bachelor's degree and pass competency examinations covering both general education and topics pertaining to their area of specialty. After a teacher is licensed, they must also meet continuing education requirements set by their state.
Mistake #3: Keeping mixed formula out too long. Formula that is sitting out at room temperature must be thrown away after 1 hour. If it is in the refrigerator, pre-mixed formula (also called ready-to-feed formula) that is opened must be thrown out after 48 hours. Formula that you mixed must be thrown out after 24 hours. Mistake #4: Re-using leftover formula.
Unopened it' can be good for up to two years. However, opened is another matter. Although bottled water is tested that does not mean it is contaminant free. Bacteria can still be present. After opening if you keep it refrigerated it should be ok for up to two weeks.