Thank you all, your responses helped. I revised my question to add a bit more about what I'm looking for. Here is a scenario that will help:
A Kindergarten- 8th grade school teaches French to all the students. There are approximately 360 students and three French teachers. The program gives students the opportunity to learn, communicate and create in a second language. The goals of the French program are:
1. To build confidence and proficiency in communication through speaking, listening, reading and writing
2. To empower children to exchange information and express ideas in languages other than English
3. To integrate French with other subjects
4. To help develop critical thinking skills unique to language learning
5. To develop insights and appreciation for all people and cultures, near and far, with whom we share the world
Here is my question:
If the second and third grade French teacher quits, is Duolingo an appropriate replacement that will allow the program's goals to continue, rather than hire a French teacher to take over?