At a Japanese entrance ceremony, the child is the main focus, not the parents. Parents do not need to stand out. At the same time, showing up in ordinary everyday clothes can feel a little too casual for a school ceremony. If the outfit is clean, presentable, and appropriate for the occasion, there is usually no need to overthink it.
If the school has a designated uniform, the child will normally wear it. At elementary schools without uniforms, families often choose something a little more formal than everyday clothes, such as a jacket, shirt, or dress. It does not need to be expensive or elaborate. The goal is simply to look as though this is a special day rather than an ordinary school morning.
Parents also tend to dress neatly and somewhat formally. For fathers, a suit is probably the safest choice, but a jacket with smart trousers can look perfectly natural as well. Mothers often wear a suit, dress, or other polished outfit, and lighter colors are not unusual.
The level of formality sits somewhere between a wedding and an ordinary day out. There is no need to dress as elegantly as you would for a wedding, but clothes you might wear for a quick trip to the supermarket can feel too casual. What matters more than buying expensive clothes is looking clean, put together, and appropriate for a school ceremony. Very flashy colors or revealing outfits can stand out more than is usual at an entrance ceremony.
There is no strict national line separating what is acceptable from what is not. Wearing something slightly casual does not automatically make it inappropriate, and a suit is not mandatory. But arriving in a T-shirt, shorts, and sandals could make people think, “But this is a ceremony.” The issue is less about breaking a dress code and more about whether the clothing shows some awareness of the occasion.
Foreign parents do not need to worry about getting every small convention exactly right. Even if their outfit is a little more casual than what most Japanese parents would choose, it is unlikely to be a major problem as long as it is clean, presentable, and clearly chosen with the ceremony in mind.