He's always peeved at how Kiyo always gets 100%, so he plots new ways to try to make sure Kiyo gets a bad mark or look bad. For example, he put a nonsense question in the pop quiz that Kiyo was sure to get wrong, and made that question worth 30 marks out of the overall score. He also gave a test with unreasonable questions but with the help from Zatch, the principal caught him.
Even after his suspension, he kept plotting to fail Kiyo. This is shown when in episode 99, Mr. Touyama tested Kiyo on very weird questions for extra credit. He also brought a new teacher to the classroom named Miss Wriggle. He believed she was the only teacher capable of giving Kiyo a failing grade, which ultimately she does when Kiyo doesn't write a haiku about being "love sick" and writes one about food instead. Many of his students including Kiyo think that he is the worst teacher ever.
He once wrote a book about Marie Antoinette and once gave Kiyo a test question asking what was the name of his cat Kiyo was able to figure out from that fact that he named it after her but shortend the name to Marie.