Enseñando would be correct
La maestra esta <u>Ensenando</u> la leccion.
Tú
You should give more context. Are you looking for a "Hey you!"? "Or a "Hey you (mean)?
Answer:
I think the word that would go there is the word " es" is there.
Yo Juego beisbol
Nosotros puedemos jugar
Nosotros empezamos ahora