One generally accepted organic practice is to continue to mulch/mow the lawn at the same height. Some yards have quite a bit of litter and need to be mowed more often or make several passes to keep from smothering the grass (as GroundKprs said). In organic yards pH is not usually a consideration when mulch/mowing leaves. What is good about mulching leaves into the soil is that they require fungi to decompose them, and lawns are woefully short on good fungi. If you cover the top of the grass with leaves and leave them for the winter, you will undoubtedly develop disease fungi under there. But when you chop them fine and allow them to drop in between grass blades, there is too much air circulation for the disease fungi to develop. The other way to get fungi into the lawn is to use a fungally dominated compost or a fungal compost tea regularly.