'I'm afraid I can't.'
'What about the next morning?'
'I'm afraid I'm all booked up.'
'Oh, really? But the exams aren't far away.'
One of the most common problems for tutors is the constant rearranging of lessons because Jemima has a dentist appointment that the parents forgot to mention or you turn up to did that little Jimmy got a detention and can't be home in time. The parents seem affronted when you tell them that we will be charged because twenty-four hours notice is not enough time for the tutor to fill in with a replacement lesson. The wealthier the parent often the more entitled they feel they are to not pay for a missed lesson.
The answer is to be very clear at the start about the terms and conditions when taking on a new client. I used to send an email with a list of conditions in which I stated that any cancellation within 48 hours of the lesson, including for illness, would result in a full charge being made. It's amazing how ill a child can be! As a freelancer, I have been subject to three parents changing times in a single week. Each one assumes that you are only teaching their child. The result is that if you aren't clear on what the terms and conditions are you will find the parents saying that they were unaware of the extra charges. You will also constantly be reorganizing your week. The whole point in being freelance is to dictate your time and working hours. Don't let the parents get the upper hand. Yes, you are providing a service but don't let yourself be treated like a servant. The kids need you.
Most of my work ended up coming through word of mouth. It is even more vital in these cases to be clear about your terms. It is very easy for professional relationships to bleed into something more casually arranged but this is dangerous because as soon as there is a problem you don't have the means to support your case.
Don't forget it's a business.