In order to avoid violating copyright laws, you need to be careful when you choose your images to share. 

Once you've searched Google Images, click on the Tools button (circled here in purple). 

Click on Usage Rights.

Then, if you're using an image for educational use, you can choose "Labeled for noncommercial reuse."

If you were going to share something more publicly, you would select "Labeled for reuse." 

Click on an image to see more detail, and then click on "Visit page." Check and make sure the site where the image is located is legitimate, and that the image has been licensed correctly.