[Staying as a microenterprise with one big customer]

Teaching English as a microenterprise.

I have one big customer (a school) and it seems possible they are going to want me to do additional work for them next year.  Which would be ok, but I am worrying about if I can stay as a microenterprise (or if the authoritis are going to insist I should be employed by the school) if I do 15 or even 20 hours a week for the school, and just 2 or 3 hours for private customers.  Is there a threshold does anyone know?  Thanks

[micro enterprise with one big customer]

Teaching English as a micro-enterprise prof liberale.  

It looks possible that next year I might be able to have have one big customer (a school) and just a couple of private individuals. .  It might be as much as 15hours for the school and just 2 or 3 private.

Does anyone know at what point the powers that be say that it's not a

proper enterprise and that I am employed (which would be problematic)

Thanks