Explanation:

We have to consider three steps:

1. Noun Student should be Plural: Students
2. Verb should be singular: has
3. and finally, their possessive case His/ their should be singular: His or Her following their Subject Number and case. 

Use “each” to emphasize individuals in a group, typically with a singular verb or noun, and it can be used with two or more items. It functions as a determiner before a singular noun (“each book”), a pronoun after a preposition (“each of us”), or an adverb to modify a verb (“They each cost one dollar”). Ensure you use a singular verb unless “each” follows a plural subject (“They each have children”).   
When to Use “Each”
To emphasize individual items or people: within a group of two or more.  
With singular nouns: when it acts as a determiner (“each student”).  
With plural nouns or pronouns: when it comes after “each of” (“each of the students”).  
As an adverb: when showing a rate or cost per individual (“They each paid $5”).  
How to Use “Each”
1. “Each” as a Determiner
Use before a singular noun, followed by a singular verb.  
Example: Each book on the shelf was a classic.  
2. “Each” as a Pronoun
After a plural subject, it can be followed by a plural verb.  
Example: The students each have their own locker.  
3. “Each of”
Follows with a plural pronoun or noun, typically taking a singular verb.  
Example: Each of the employees received a bonus.  
4. “Each” as an Adverb
Modifies a verb, indicating an action performed by each individual.  
Example: They each brought a dish to the potluck.  
Common Mistakes to Avoid
Using “each” with a plural noun: directly (e.g., “each students” instead of “each student”).  
Forgetting the singular verb: when “each” is the subject or before a singular noun.  
Confusing “each” and “every”: “Every” is for groups, “each” is for individual elements within the group.  
Using “each and every”: While used for emphasis, it’s considered redundant in formal writing. 

Is ‘Each’ Singular or Plural? How to Use ‘Each’ Correctly?

What is the rule for using each? 
 
The word “each” refers to every one of two or more individuals or objects within a group. “Each” typically describes countable nouns (which you can represent in singular or plural form), rather than uncountable nouns (which cannot occur in plural form).

Does each is singular or plural? – singular
 
“Each” is often followed by a prepositional phrase ending in a plural word (“Each of the students”), which confuses the verb choice. Each, too, is always singular and requires a singular verb.