I have my master's degree in Science Education & Communication.
I have been designing educational content (workshops, classes, complete curricula accross) for science education and English (ESL/EFL).
For this I have been researching and implementing all kinds of (digital) innovations in education.
I am also an avid user of a multitude of digital apps for classroom application (PhET applets, digital/electronic learning environments, socrativ, etc. )
Reach out to them saying "it's been a while" and you're just touching base.
Then try to find out what their frustrations are, what they've tried to solve it, why it didn't work, what they would do to get the problem solved, and what one big question they'd want to get answered.
Then build a product around that need and do an internal launch preceded by 3 vids that already give them great value and part of the solutions.
Build an opt-in page and drive the people from the list there.
Host a free webinar.
Then open cart.
then sell your product.
the day before your cart closes, email people from your dorment list, remind them the cart is closing and they can still get the product.
repeat around 3 and 1 hr before closing cart.
Statistically speaking, a pool of 30 respondents is enough to start seeing a trend. 100 is about the maximum. Beyond that it's just more of the same pattern and it might even start getting confusing, because the differences will start to level out.