I will teaching Computer Science Discoveries and wanted to run through this free online course. I am enjoying it so far. I think for 8th graders, I would probably teach “repeats” (“loopy”) using a line dance such as the electric slide. I would ask the students to write down the steps to the electric slide. Then rewrite it using repeats. Then teach the class as a whole, getting everyone up and moving.
Then review the words iteration, repeats and loops.
So, currently I teach PK thru 1st grade. Loops will probably not be a topic that I introduce to my students as a whole class. If I worked with the students more than once a week I would introduce this idea to challenge certain students. Initially I think I would start by having the students look for a pattern. Kindergartners are introduced to patterns and I believe that it is continued in first grade. But they have a basic understanding of AB… etc patterns. They might be able to break it down that way. Once they identify the pattern, the introduction of the loop should be fairly straight forward. That is the theory. Since I have not had the chance to try it out I am not sure if it would actually work. Mainly at these early elementary grades focusing on the idea of sequences is pretty good.
I teached loop for my students with example : we sing a song. Sometimes when we sing a song, there are some phrase, which should be repeat.
Ex. Are you sleeping song
Are you sleeping -------> Are you sleeping 2x
Are you sleeping
instead of write it down in two lines, we can use 2x.
it is really helpfull and fun too 
I think the best way would be to ask them to reflect on the things they do over and over again. It can be any process that they do repeatedly such as getting ready for school, or learning a skill.
I use small flash cards with code such as below
Loop
Place color1
Place color2
Place color3
End-Loop
Place color4
I use little color cubes or small color toys and students pick their own color1, 2, 3 and 4 and then place the cubes to match the loop logic. I explain how color 4 is not repeated as it is outside the loop. My students range from 6 - 12 years. I purchased the color cubes and color penguins in Amazon long back. They are available under ‘counting toys’ search. Hope this was helpful.
I have introduced “loops” to my Grade 4 as “patterns that has repetition” I pair them into groups of two, one pretends to be the “robot” and the other a “programmer.” The programmer must want the robot to go somewhere around the classroom and find him/her something. And all the programmer does is say the directions “move forward, move backwards, turn left, turn right” until the robot reaches the destination.
I think the best way to introduce loops to my 6th graders is through dances or robotics.
I think, I would use the video " Getting Loopy" to help the students to understand loop concept. Then, strengthen the understanding with the iteration activities which is not only fun but very practical to define the concept.
Music patterns. Such as showing the repeated pattern that music uses to structure a song. Then take a 30 portion of that song and mix it with another 30 second song clip. When you mix these together we are creating a loop.
With students we could have 4 rows(numbered Row 1, Row 2, Row 3, and Row 4). The odd numbered rows would replicate one drum beat (ba diddy ba diddy diddy diddy ba) while the even numbered rows would replicate another drum beat (ba dun dun dun, ba dun dun dun). We could add step into the loop and pen beats or tapping.
I would use the video as well! It will be a fun introduction before showing the kids how to use dance and repetition to complete the loops.
I love the idea of getting the students up and dancing, because so many students learn at different levels and by different strategies! Plus it’s would be fun when they begin seeing where the loop starts over again!