How much time for freestyling?

in my opinion alice is a great tool for interested oriented work of pupils but i've found students with under average skills get stuck soon when left on their own pursueing a personal project

i would like to share opinions on the proper balance between led activities i.e. "see how this method works" and autonomous, yet facilitated, time

I generally follow a model with my intro students:

1) Discuss the problem (monitors off).
2) Talk about the possible approaches to the solution.
3) In alice, create a simple world that demonstrates the new approach on the digital projector, explaining the new steps. In the case of recursion, for example, I make a bouncing ball whose height slowly tapers off.
4) Circulate to ensure students have a working version, and that they can explain why it works.
5) Assign a small project (~20-80 minutes, depending) to students to have them implement the new idea with some old ones.

At about the 1/3-1/2 mark in Intro 1 and Intro 2, I assign a "do what you'd like; impress me" project for the students. I grade it on progress after 2-3 days, but give them an opportunity to tune it regularly throughout the term.