It sounds like you found a good solution to your problem. With respect to the issue of wind speed versus height, you might need to give some additional clarification in your presentation.
Before I started this, I assumed like others it was the wind speed that caused the turning.
I think that "wind speed" here refers to the wind speed measured at the ground surface. This is an important distinction that should be made clear. Otherwise, your audience might get confused, or think that you have misunderstood the concepts when you also state:
In the books they say it is also the height since the lower to the ground it is, the more chance of the wind being blocked by hills, homes, etc.
This is another way of saying that air velocity (or wind speed) is higher at the elevation of taller windmills. The higher air velocities tend to result in faster rotation.
For your own experiment, it seems as though you are using the rate of rotation of your turbines as indicators of air velocity. The question becomes whether the air velocities in your experiment are similar to the real-world scenario described by the books, where obstacles & friction result in lower air velocities close to the ground (or table top, or whatever you used). If your velocities do not match the expected relations (it sounds like the taller turbine was not the fastest?), why not? Did you lack tall obstacles? Did you use a fan that might direct air in a certain direction? What implications does that have for your experiment and for real world use of wind turbines? These are examples of the sorts of issues you can raise in your presentation. Also if you identify a flaw in your experiment while considering these sorts of questions, you might be able to rerun your experiment to correct the flaw.
I hope that helps!