I think we often expect kids to see subjects and predicates before we've taught them their parts. Assuming they already can identify nouns and verbs...First, teach the state of being verbs...I mean have them memorize a list of them in a specific order such as: be being been am are is was were do does did have has had can could will would shall should. Post the list on the board by clustering them into their sets. Next teach prepositions. Again, teach a preset list of prepositions. Some lists have only the 20 most common, others have as many as 60 or 70. Choose the list best suited for your grade. I taught 60 to my 2nd graders. Post the list in your classroom. NOW your students are ready to look for subjects and predicates.
1. Look for the prepositions. Circle them. Ask "What" to find the words that belong to them (around...around what?...around the yard) Draw an oval that includes both the preposition and its object (it will look like a big closed safety pin...so I told my kids to "pin" the preposition), The preposition and its object will not be part of either the simple subject or the simple predicate so they can be eliminated.
2. Look for and action word. If you can't find one, look for a state of being verb. That is probably your simple predicate. Double underline that verb.
3. Look for a noun that is not in a "pin". Find the noun that goes with the verb and is the "who" of the sentence. (I taught them to refer to anything doing the action as a who, even if it was the desk,) Underline that noun.
4. Look for another noun--there may not be one, but if there is--that is getting something done to it. That is your direct object. Put it in a box...it belongs to the predicate.
5. Say just the simple subject (who noun) and the simple predicate (action or state of being verb).
6. Say the part of the sentence that goes with the simple subject. (complete subject)
7. Say the part of the sentence that goes with the verb. (complete predicate.)
This sounds quite involved, but actually simplifies finding the subject and predicate when they can eliminate parts of the sentence. I've taught it this way to first graders (YEP...first graders!!! ok, they were high level first!
and recently helped a 7th grader who was having trouble finding subject and predicate and found that it made it so much easier once you got rid of all the prepositional phrases and the direct object.
I know a lot of teachers would balk at teaching all seven parts of speech in first or second grade, but when I did it made teaching writing so much easier...they knew what I meant when I said they could make a sentence more interesting by adding a prepositional phrase about the boy, or that they needed to have an action verb instead of state of being verb...It gave them the language of writing so that they could talk about what they were doing. Why we delay this, I don't know...we teach them math words like add and subtract, sum, difference, equal...but we shy away from teaching language words like preposition, conjunction, and such....
OK...I sorta got off on my soapbox there, didn't I!!! Can you tell that I love to teach English and writing???