Kodable

Kodable is possibly the most user friendly of the sites. It is geared to younger students. You can set up classes then create accounts for you students. Track your students' progress as well as see what standards each student has completed. They now have curriculum learning guides that have lessons, vocabulary, and activities you can do with the students that go with the lessons you have assigned them in the program.

Kobable has Hour of Code lessons here: https://www.kodable.com/hour-of-code#lesson-plans
The lessons are grouped by grade level for grades. There are even lessons you can do OFF LINE!! So not enough computers, no problem!