Are you teaching double-digit subtraction with regrouping?
Are your students SO EXCITED about regrouping that they are regrouping everything??
When I saw this problem in my own classroom, I created this sort. Based on a subtraction with regrouping poem, students sort 18 problems into three groups: need to regroup, don't need to regroup, and identical digits.
This will help your students stop and think before they start to subtract. It will also ingrain the poem into their heads to help them figure these problems out independently!
For more information, and to see this activity in action, please visit my blog