DS is 6. We send him to school with fresh fruit (berries, apples, bananas, peaches, plums, pears, kiwis, clementines, etc), dried fruit (raisins, craisins, dried cherries, prunes, apricots), nuts (almonds mostly), veggies (green beans, sliced green or red peppers, celery, carrots, fresh peas, cauliflower, broccoli, edamame, seaweed salad), occasionally humus with brown rice crackers, occasionally fresh guacamole (it turns color so not that great if it won't be eaten quickly). There are so many different fruits and veggies that I don't see a problem with these being the great majority of his snacks.
We don't do all those 'healthy' prepackage granola type snacks (loaded with sugar even if they are organic) or a lot of baked goods (most quick breads like banana and zucchini bread are loaded with sugar and often fat). If we do yogurt, we do plain and add fresh chopped fruit. The fruit yogurt (also the vanilla) is LOADED with sugar (yup, the organic and 'kid friendly' kinds too).