So, as we have a similar club setup, and we both have crazy labs, I hope you don't mind me sharing a couple of tips that it took me waaaaay too long to discover. Of course, feel free to ignore if you don't feel that they're relevant
1. When you arrive and feel like you have a kangaroo on methamphetamine at the end of the lead, feel free to give yourself a bit of space. I used to just hold the end of the lead and the second Ella glanced in my direction, I'd mark and reward. Over time, the lunacy decreased and the length of time it took to calm down decreased.
2. Don't be afraid to modify the tasks to suit your needs. As long as you don't affect the class, the instructor is highly unlikely to mind. For example, I still find that Ella takes a little longer to warm up into work mode than most dogs. When we all line up and start a heel work pattern at the start of class, I usually hang back a few metres and warm Ella up aside from the group. Then, when she's starting to work nicely, I'll slowly work our way back into the group.
3. Take a break when you need to. I find that Ella's attention and excitement levels still need to be managed so I'll often take a break after an exercise race off to the side of class and play a quick game of tug to reward and release the excess energetic before rejoining the group. Another example from this morning is that Ella was suddenly totally excited and unable to focus. We had just split into four groups of 5/6 and lined up side by side. We set up an agility jump in front of each line and then there was a bowl a couple of metres after the jump. Off-lead, we heeled towards the jump, put our dog in a sit-stay, walked around the jump, placed some food in the bowl and walked another couple of metres past the bowl. Then, we called our dog over the jump, past the bowl to us before releasing back to the food in the bowl. Then we'd heel back to the end of the line and repeat. Ella's mind was blown and she reverted to kangaroo on methamphetamine at the end of the lead

. So, we stepped to the side of the group and just watched. After a while, she calmed down and I was able to join in and perform the exercise. However, between each turn, we didn't join the end of the line but instead, stood out to the side and waited calmly with a bit of space to ensure she didn't get over the threshold again. Taking a break and modifying the exercise had no impact on the others there but meant that the loony lab could work in an environment where she could focus.
Anyway, I've babbled on enough now

sorry!