There is a fraud going around where you will receive an email from someone wanted to book lessons in advance. They inquire about the cost and eventually send you a check in excess of the amount before the lessons are scheduled to begin. They ask you to refund them the difference.
The problem is that the check they send you is fraudulent and even though it might clear initially, eventually it will come back. You may even be liable for cashing a bad check. More info can be seen at http://en.wikipedia.org/wiki/Advance-fee_fraud
Do not get involved with these folks. They are part of an international ring of scammers. There is an ongoing investigation by US federal law enforcement. If you have been a victim of this, please contact your local authorities. In the US you can also contact your regional FBI office ( http://www.fbi.gov/contact-us/field
) or even the Secret Service ( http://www.secretservice.gov/ectf.shtml
) which is involved in currency fraud and internet crime.