I’d ask anyone who is criticizing PBL in the classroom to talk to the teachers and students who have had this opportunity. I’d ask them to look at what students are creating, making, and building during this time. I’d ask them to talk to the parents about their students’ attitude towards learning.
I give two answers to the question above:
Try it for a day and see what happens. Start small and build from there.
Teach through the project, instead of using the project as an “end-of-unit” assessment that takes more time than a multiple choice test. When kids learn during the project, the time constraint goes away.