Legally you cannot do. But I don't think any one who do at home is registering as it becomes business and bound for legal fees which might end up to a good amount, which you will not bear it. Apart from that there are many legal obligations you have to take care of and home will not be accepted as a business point by authorities.
Only nurseries and kindergartens do it legally.
You can do it as long it is safe, even the authorities will not trouble you, untill unusual happens.