Season 2: Episode 32: From Nurse to Worse
Zack develops a crush on his school nurse, and he couldn't have pick a worse time. Soon after he asks Kelly to go steady, he falls for the school nurse. Thankfully, Zack has friends who help him through his hour of confusion. The gang, minus Zack and Kelly, get the nurse to help set up Zack, so he'll go back to Kelly.