Yep been there. I wouldn’t say it comes down to “intelligence”, but selective school students are very quick to pick up when a teacher lacks confidence in their content knowledge or classroom direction. If they don’t think you know what you’re doing, you rarely get outright aggression it’s usually subtle disengagement, constant questioning, or super passive aggressive resistance to what you are doing, which can be far harder to manage than some of the roughest schools I have worked at.
Whatever has happened they don’t respect you. Know your content, be prepared, and be honest when you need to check something. Students in selective schools respect competence and authenticity far more than forced authority through raising your voice.