Academic inflation is when grades given at schools and universities get higher, even though the work people do may not have gotten better or harder. It means that over time, an A grade will become easier and easier to get, and the same is true for a B grade and so on. This means the grades for the same amount of effort become inflated. Imagine if all the money in the world suddenly doubled in value - it wouldn't be as valuable as before because it would take twice as much money to buy the same thing. That's what happens with grades in academic inflation :)