A simple sentence is made up of a single independent clause, e.g.: Do you play football? One more example: The bus was late. A simple sentence contains only one independent clause. An independent clause is a group of words that has a subject and a verb and can stand alone as a complete thought.
The resources above cover the following skills:
Conventions of Standard English
Begin to demonstrate command of the conventions of Standard English grammar and usage when writing or speaking. [L.K.1]
Produce and expand complete sentences in shared language activities. [L.K.1f]