Google classroom is a fantastic tool to use for classroom content.  It's a great way to keep kids on track and organize educational resources so they are accessible in and out of the classroom.  My favorite new tool just made my life much easier.  The new Rubric feature allows for complete descriptions of expected outcomes and makes it easy to grade projects. Type in your various levels and point values, and grade easily once students turn in work.  It makes it much easier to communicate to students about their projects as well.  They can see exactly where they succeeded and where they need to work harder. 

I think teaching selection tools in Photoshop is one of the most difficult tasks to do in a class of 24 students who are all at different levels of understanding.  First of all, Photoshop can be a super intimidating program to use, let alone teach 14 and 15 year olds how to use.  

First, don't reinvent the wheel.  Adobe has tons of tutorials to use that offer step by step instruction and also have the practice photos to go with them.  We used this set of tutorials to learn the quick selection tool, adding and subtracting from selections, and fine tuning selections.

Our lesson to demonstrate mastery of selection tools is a lesson on Pop Art.  Students use their own self portraits to make selections and color fills to create a Pop Art Self Portrait.  First everyone practices with the same image that I give them.   In order to allow students to work at the correct level I break the entire lesson down into parts and pre-record all the steps.    Students who like to work ahead or on their own can do so by following the videos that I have posted in Google classroom or via a QR code displayed in the room.  I still teach step by step and explain things along the way, but allowing students to work ahead gives them a a better sense of how the program works, and puts them in a position of being help classmates out.