小子放学你给姐等着
[xiăo zi fàng xué nĭ jĭ jiĕ dĕng zhe]
In casual slang, the sentence could translate into English as 'Kid (usually addressed to boys informally), wait for me outside school (so I can do something with you)!'. A bit aggressive, showing a bold personality, maybe someone ready to challenge anyone after school ends. Often used humorously by people pretending toughness or planning playmates after classes.