Teachers, parents, educators: Where do you stumble?

Hello Instructables!

I currently run a small business in which company teachers travel to local elementary schools and teach project based engineering.

For us, it's second nature. But I recently learned that it's not always so easy to implement project-based learning in the home or at school.

What are you challenges in this arena? Is it getting the right materials? Finding good instruction? Making something scalable to a 30-student classroom? Let me know so I can learn how to better help the community :)