Mid-Prac Exhaustion

I'm three weeks into my prac, with two weeks to go. I'm feeling flat tonight, having sensed my mentor teacher's possible disappointment with some aspects of my performance. There's no doubting I put the hours in when it comes to preparation - I have my lesson plans chunked down into 10-20 minute intervals, addressing learing outcomes, taking inspiration from my school's favoured unit planning framework, allowing space for reflection, and so on. But my weak point appears to be behaviour management. It's not so much that I don't know what to do, but that in someone else's classroom, with someone else's rules, I don't feel comfortable enforcing my expectations.

In my placement I'm teaching two different teacher's classes; one teacher is laid-back, cruisy, with a level of patience I envy and a seeming ability to tune out from the noise level of the classroom. Her students are boisterous, chatty, cheeky, and often just plain rude - but loveable nonetheless. My other teacher seems to accept less "problem" behaviour, and expects me to as well, which is fine by me - but I don't seem to have the control I need in her classroom. Students disregard my instructions or answer back, and I'm reluctant to escalate my response to the point of a power struggle, when a low-key response should be enough.

*sigh*

I'm also finding that I need to provide far more scaffolding than I anticipate - even for older students who I would have thought were capable of being more autonomous than they are. I seem to keep failing to chunk tasks down into small enough bites for them to manage - but I feel like I'm holding all their hands through tasks that really shouldn't need as much structure and scaffolding as I have to provide. What I'm wondering is, at what point does scaffolding become hand-holding?