I have a 6th period class with three or four of those types of students.. they were truly holding back the rest of the class.
To help fix this issue I started grouping them near me in the same area. When this happened the first time in class, I would give the rest of the class a problem to try alone - then I would do a more guided example with just those students. This would help the ones that really needed help.
Then if it happened again I would have every student cover their eyes and vote:
Hold up 1 finger this means: I understand and I am ready to work alone
Hold up 2 fingers this means: I need to look at my notes, but I think I can do it
Hold up 3 fingers this means: I can't do this, I need to see another example
If I had a lot of 3's then we did another example - if the whole class is lost what is the point of pushing through?
If I had a lot of 1's and 2's then I passed mandatory tutorial passes to the students who were behind, and pushed through with the rest of the students. It is amazing how mandatory tutorials have helped their math knowledge, and self confidence...