Yes! We have a free course in CodeCombat and a free unit in Ozaria.
CodeCombat - Our Introduction to Computer Science course does not require a purchase. It contains 44 levels and takes 1-3 hours depending on your students' ages and experience.
Ozaria - The Prologue: The Sky Mountain is free and does not require student licenses. It takes 1-2 hours depending on your students' ages and prior experience.
There is no limit to the amount of students who can participate!
Please feel free to try it out in your school or district.