If you have a class on the last lesson of a day, especially towards the end of the week, your plans need to be extra flexible.
At that time of the day, students are tired and are often ‘coming down’ from the sugar rush of lunch. I found out at teacher training, if I had potatoes at lunch I had zero desire to do card sorts.
Of course you do not want to ruin your relationship with this class, especially if you only see them twice a week or so. Have as little in the lesson where they have to listen to you as possible. The time to work on their attention span is practically any other period in the week! If you must lecture them, for them to be able to access your lesson plan and you only see them at the end of a school day, consider filming that part of your teaching beforehand so they can watch it for homework the night before.
There are two possible ways you can go with your group: you can do something active and high energy or you can do something a bit more passive and comforting.
Active and high energy lessons usually (but not always) require students to be out of their seats. They could role play or mime concepts. They can do big puzzles in groups. They can move around the classroom to vote with their feet during a debate. If you want them to stay seated much of the lesson, you can ask them to prepare to teach their peers on a topic, then have them ‘exchange lessons’ at the end.
Sometimes, and you will be able to tell from their body language, they need a break from all that and need something more quiet to do.
These are the times you can give them book work activities. They can do exercises, they can convert text into diagrams (or vice versa), they can read the textbook to each other and paraphrase the paragraph. You can also give them other quiet activities, like making infographics for display, making charts or graphs; or writing. Be prepared to circle the classroom the entire lesson, to keep up their motivation. Have a couple of activities that take a couple of minutes to break up the lesson into chunks.
At the end, have some sort of a game that reinforces your lesson objectives. Bingo works well if you haven’t got many resources, as do group quizzes. You can also make games online for students to play if they have tablets or laptops. This is to make sure the lesson doesn’t fizzle out with everyone just staring at the clock.