Consider elastic waist pants or other closures that are easy to open and close to make bathroom time easier. Also, by having items that are easy to put on will make it easier for them to be able to dress themselves and become more independent. Avoid white and light colored clothing that will show stains more. Purchase a variety of items that match and can be worn with different items for a number of outfits.
Choose shoes that are durable and comfortable when they are playing. Leave the fancy shoes for special ocassions. Check with the teacher to see which shoes are preferred. In some cases, they want children to wear tennis shoes instead of sandals. Depending on your climate you may want to purchase items that can be layered. A light jacket can be used in the morning and taken off when the weather warms up during the day. Ask the teacher if shorts are permitted and it there are any clothing items that are not permitted for children to wear. Children may be more willing to wear clothing items that they had a part in the decision making when purchasing items.