I don't know a lot but I just did a class about this.
But to change perfect past tense completed in the past by changing the verb is or could be by replacing the verb with the action to was ,did ,before, ect. I think this might help
Some colleges require that each potential student completes an essay.
Subjunctive mood is defined as the verb form used to express a wish, a suggestion, a command, or a condition contrary to fact.
To convert the above sentence into a subjunctive mood, REPLACE REQUIRE WITH PROPOSE.
Some colleges propose that each potential student completes an essay.
In this case, propose means a suggestion.
