Old Man Teaching System?!

James was a very popular online male model with millions of admirers, he dies a hilarious death in the shower, the god of reincarnation thought it was hilarious and reincarnated him into an old man who is a teacher, as a gift the god of reincarnation sent him the "Old Man Teaching System" How is he to adapt?! System: Host must teach the children like an old man would! James: What? Okay, the square root of- System: No! Explain it like an old man! James: ??? Follow his daily life of being an old man, doing things ranging from tending to his garden, protecting his lawn from children, and teaching annoying teens.