Differentiation is key to reaching all students. Lots of group creators on the web will help you randomize your students, but the Group Creator Spreadsheet makes homogeneous and heterogeneous groups and pairs based on performance data you provide. And since it is a spreadsheet, you can re-sort it in a flash to create different groups for later in the day or tomorrow.
The sheet comes with directions on the first tab and fake students so you can try it out, but then you add your own students names. It starts with one score column, but you can have as many "score" columns as you like. Call them reading, writing, or label them by the common core standards your students are working on. Re-sort, re-rank and re-group your students as often as you need to.
Use "Save As" to create multiple copies of the sheet if you are a secondary teacher with multiple classes. And if you prefer it as a Google Sheet, there is a link on the spreadsheet to get the Google version.
I am super excited about this product. I created it for myself and I use the Google Sheets version of it at least three or four times a week with my high school English classes, but it is great for ANY grade level.