Hi Monica!
That's a very good question! There are so many
theme park attractions with varying height restrictions at
Disney World, it's hard to get a true accurate picture. You also have many attractions with
no height restrictions of any kind, so there are those attractions to bear in mind as well..
Disney does an incredible job at ensuring there's a little something attraction-wise for everyone, regardless of their age or height, thus they do a good job equally spreading attractions over a wide spectrum of height restrictions, to best accommodate nearly all guests. There are those with height restrictions anywhere from 32 inches (or 3 feet), 48 inches (or 4 feet), so on and so forth.
If you were to ask me to make an educated guess, however, I would say the majority of attractions with height restrictions on average is somewhere between 44-48 inches; or the ballpark of 3 1/2 to 4 feet tall.
Hope this helps. Have a magical day!
Terry