I've discovered that using 3 x 5 cards is the best solution, especially when the child will be moving from one location to another during the school day. Loose cards are hard to manage, but there are now systems you can use to keep them organized and attached without spending significant amounts of money or adding bulk. Here are a few suggestions:
Try a system of spiral bound cards. While the order can't be easily changed, they will stay organized.
Purchase cards with holes and use rings to attach them. There are several different types, some that use one ring and others that have two or more. Cards can be moved around, but they are also easier for the child to tear off.
You can also purchase small notebooks for your cards. Harder for the child to remove, re-positionable, but also slightly higher in price. You can find each of these options at your local office supply store.
What system have you used successfully?