kapur.arnav wrote:She recommended that each student bring his or her homework every day.

The indicative conjugation would be "each student brings," but since 'recommended' triggers the subjunctive, we use bring.

Can someone please elaborate this rule... Thanks!!

Use of the Subjunctive

We use subjunctives mainly when talking about events that are not certain to happen. For example, we use the subjunctive when talking about events that somebody:

wants to happen
hopes will happen
imagines happening
Look at these examples:

The President requests that you be present at the meeting.
It is vital that you be present at the meeting.
If you were at the meeting, the President would be happy.

The subjunctive is typically used after two structures:

the verbs: ask, command, demand, insist, propose, recommend, request, suggest + that

the expressions: it is desirable, essential, important, necessary, vital + that
Here are some examples with the subjunctive:

The manager insists that the car park be locked at night.
The board of directors recommended that he join the company.
It is essential that we vote as soon as possible.
It was necessary that every student submit his essay by the weekend.

Notice that in these structures the subjunctive is always the same. It does not matter whether the sentence is past or present. Look at these examples:

Present: The President requests that they stop the occupation.
Past: The President requested that they stop the occupation.
Present: It is essential that she be present.
Past: It was essential that she be present.

Subjunctives also appear in contrary-to-fact conditions and in some idiomatic phrases like God save the Queen and Heaven forbid that she try something new (in which both "forbid" and "try" are different uses of the subjunctive).