I just want to say I feel all of your pain with the toughness of Afterschool classes. I have 29 students in mine, and it's a daily battle to get them to care about any activity I try to offer them. I think this opinion activity is worth a try and could be fun, though.The most I've gotten their attention is when I tried to give a rallying speech about how close all of them are to being really great English speakers. I'm truly amazed at how huge their vocabularies are, but how little they've practiced any grammar. If they practiced grammar just a tiny bit, it seems like they'd all be able to speak so well. My latest tactic is to teach one small grammar point a day and just try to convince them of why they should learn it. I usually start with "one day you will all go to a foreign country!!!" which usually gets their attention, and then "and people will ask you such and such" and then I think of actual conversations they will one day have with a foreigner, and they will shout out to me how they will answer. I wish the class was more student-centered, but to be honest, I usually have the attention of about 6-8 students out of 29 every day. I know this is terrible, and i want it to be better, but this is where I am at right now.