Same. My grandmother taught me how to solve equations, and we'd do it for "fun" on the bus in Moscow; I was in, at most, fourth grade. And you know what, it was fun, and it wasn't hard.
Granted, she was also a programmer, and my grandfather was a mathematician, and both my parents were engineers - so maybe my baseline for fun and education was set differently.
I doubt you're a bad grandson, but I'll share this story with you.
I was raised by my grandparents, and I had enormous respect for my grandfather, who was the most badass human being I've ever known, though you would never know it to see him. He was very quiet, he spoke little, always watching and listening.
He was in his 50s when I was born and lived with them permanently when I was 5 years old. He and my grandmother were my parents.
They were always patient and kind, and always stoic about everything. One day while camping my grandpa was sitting next to a dart board, and one of the darts I threw went crazy wild; it hit and stuck deeply into his left calf. I just stood there with my mouth open while he puffed his pipe, staring at me. After a couple of moments, he calmly pulled it out, wiped the blood off of it, and carefully tossed it back to me, saying, "Careful where you throw those, boy."
I always had a lot of respect for them, though I didn't show it. In fact, by my actions, I took them for granted.
They both died of old age when I was in my 30s, even as I was just starting to truly appreciate them.
Now, many years later, I would give almost anything to be able to spend another day with them. There's so much I'd ask, so much to learn.
In summary: spend as much time as you can talking to your grandparents while you still have them, because once you're old enough to really appreciate their value, they might be gone.
Granted, she was also a programmer, and my grandfather was a mathematician, and both my parents were engineers - so maybe my baseline for fun and education was set differently.