English Worksheets Land
English Worksheets Land: Inappropriate Shifts in Verbs
Find fifteen worksheets designed to provide practice on maintaining verb tense. These exercises have been created expressly for elementary students. All worksheets are available as PDFs.
Grammarly
Grammarly Blog: Verb Tense Consistency: Grammar Rules
This page focuses on the need for verb tense consistency on a clause level. It is important to maintain the same verb tense in a clause; if the time changes, use a second sentence.
Other
Indiana University of Pennsylvania: Writing Center: Shifty Tenses
Notes about verb tense, when it should and should not be changed, and what tense is best to use when writing about literature.