Don't assign the whole unit. Use a PDF editor (Adobe Acrobat, Preview) to extract 2-3 pages per lesson. Example: Le Mag 3 Unité 2, page 18-19 (grammar practice: le futur simple).
Additional teaching resources and guidebooks can be found on the Hachette US Education portal specific answers to an exercise, or would you like to know more about the audio materials that accompany this level? Le Mag' 3 - Livre de l'élève (Grand format - Hachette FLE le mag 3 cahier d 39-exercices pdf
which often includes answer keys for the workbook exercises. Where to Purchase Don't assign the whole unit