Possible Noticings for Sentence #2

This is a compound sentence.  

You need both the comma and the conjunction to join what could be two separate sentence. 

It begins with a capital letter and ends with a period.

It is a statement.

2. The bell rang for first period, 

(article, noun, verb, preposition, adjective, noun)

[Bell is the subject of this part of the sentence.

Rang is the verb/predicate.]

and the students herded noisily through the door.

(conjunction, article, noun, verb, adverb, preposition, article, noun)

[Students is the subject of this part of the sentence.

Herded is the verb/predicate.]