Most times you can create a Google document and easily hand in your work to your teacher using Google Classroom. There are some assignments though, such as solving math problems or drawing a picture, that need to be handed in as an image.
1) Take a photograph of your work using your phone
2) Open the Photos app.
3) Tap the Select button, then tap each photo or video that you want to share.
4) Choose "Google Drive" as the share option.
5) Pick "Select Folder" option.
6) Choose "My Drive"
7) Select the folder you wish to save the image and tap the "Save here" option.
8) Now you can go to your Class and select that image from your Drive to turn it in!