Controlling settings, permissions, and membership within Teams and channels
Hello Donnie,
My name is Juan Pedro, I am an Independent Advisor and consumer of Microsoft products. I will be more than happy to assist you today!
I am sorry to be the person bringing the bad news, unfortunately, this is not an option.
However, you could download a timer to your device and share your screen for your students to see the timer.
I hope this helped. I will be around in case you need something else.
Thank you.