"Sarah wants to go home now" is actually in the present simple tense, not the present continuous tense. In the present simple tense, the verb "want" is conjugated as "wants" for the third person singular (she, he, it) form. So, "wants" is correct in this sentence to indicate that Sarah currently desires to go home.
"Sarah wants to go home now" is actually in the present simple tense, not the present continuous tense. In the present simple tense, the verb "want" is conjugated as "wants" for the third person singular (she, he, it) form. So, "wants" is correct in this sentence to indicate that Sarah currently desires to go home.