The teacher warned the students that any transgressions of school rules would result in punishment.

transgressions 是名词 transgression 的复数形式。transgression 由前缀 trans-（表示"跨越"）和词根 gress（表示"行走"）加上名词后缀 -ion 组成，字面意思是"越过界限"，引申为"违反、违规"。 transgressions of school rules 指"违反校规的行为"。