A lvl 5 baker produces 3920 bread/24h from 2.66 baskets, 3920 water, 1960 wheat. A school makes 12 per 24h, thus 300 bread. However - 300 bread at 8/stack = 6gc production in 24h (not including prov house time)
A bakery has 3920/400*8= 78.4 gc in production, but also faces the following costs: 13.3gc in baskets, 33.6gc in wheat, and 14.7gc in water, for a total of 61.6gc in cost. Thus its net income is ~16.8gc per 24h. However - a school is more efficient then a watermill, a well, cokers, and many other buildings. Bakery is one of the higher profit buildings for its space occupied (though its license count profit is not quite as good, given some like farm take up more then 1 space due to fields/silos, but have better 24h profits).