It is possible that Mexico may be a less developed country than your own. You may feel sleepy or tired the first few days. You body is adjusting to the higher altitude. This will pass quickly. Your stomach is also adjusting to more fresh food and a different time pattern of food.
Courtesy is of great importance.
Greet and say good-bye to people with handshakes, embraces or cheek kisses. Communication and consideration are of great importance. If you need a sack lunch for the next day, tell your family a day ahead. Be very clear about what time you need to be at school for excursions. If you will be going out to dinner or missing a meal, tell them your plans.