posted by Anonymous .
vas a la clase de ingles en la manana o en la tarde?
Although orally, from native speakers, you may hear "en la mañana" that is not the grammar to use.
¿Vas a la clase de inglés por la mañana o por la tarde?
If you don't understand EXACTLY what I wrote, ask, please.
(with no specific time it is "por" and with a specific time it is "de" but only less correctly will you hear "en."