Common options:
* Voy a la escuela los lunes. (I go to school on Mondays.)
* Voy a la escuela los días de semana. (I go to school on weekdays.)
* Voy a la escuela los sábados. (I go to school on Saturdays.)
* Voy a la escuela los domingos. (I go to school on Sundays.)
Less common but possible options:
* Voy a la escuela los fines de semana. (I go to school on weekends.)
* Voy a la escuela los días de lluvia. (I go to school on rainy days.)
* Voy a la escuela los días de sol. (I go to school on sunny days.)
To give a more accurate completion, please tell me:
* What is the context of the sentence? (e.g. Are you talking about a schedule, a preference, or something else?)
* What day(s) of the week or what specific time period are you referring to?
Once you provide more information, I can give you a more tailored and relevant completion to the sentence.