This was an idea I learned from Miss S. who teaches younger grades:

When the kids are quiet,  I hold up 1 to 10 fingers over my head.  They have to hold up their fingers over their head to make a combination of 10.  For example, if I hold up 2 fingers, they hold up 8 fingers.  If I hold up 6 fingers, they hold up 4.  They cannot talk as we do this.  They are doing this as they are lining up.  In between problems, I say “erase.”  Sometimes I just hold up the fingers, and they start quietly lining up while doing the math combinations. This is a great way for them to learn combinations to 10 AND line up quietly at the same time!