Final answer:
The correct form of the verb estar in the sentence is estás. It is used to express location or temporary states.
Step-by-step explanation:
The correct form of the verb estar to complete the sentence is estás. The sentence should be: Yo estoy en la clase de español con la profesora, pero tú no estás aquí.
The verb estar is used to express location or temporary states. In this sentence, it indicates that the speaker is in the Spanish class, but the person they are talking to is not present.
Here's an example to illustrate the use of estar: Estoy en el parque con mis amigos, pero tú no estás aquí.
Learn more about Verb estar in Spanish