Kano PC - Second Monitor

We purchased a Kano PC for e-learning this year. Everything has been going well except the screen is a little small to be doing split-screen with the class on one half and the school work on the other half. I hooked up a monitor I had around the house and everything runs suuuuuper slow and clicks lag really bad. I have checked to make sure the refresh rates or whatever are the same but I am not sure what else I can do, or maybe the Kano PC just can’t handle an extra monitor?