The answer is, yes, if all of the elements of a contract exist. A contract exists when there is an offer and an acceptance. Acceptance can be demonstrated by any statement or action that indicates you have agreed to the terms of the offer. For instance, if your friend said, "I will teach you how to drive for $100 an hour"; and you say, "Let's start today"; there is an offer and an acceptance and a contract has been formed.
I realize it is rarely that simple and straightforward. If you don't say "yes" but allow your friend to teach you to drive, the law will generally uphold your friend's right to be paid. In other words, acceptance could be signified by your actions, not just by a statement.
Perhaps more often, there is no agreement on what the terms were. Your friend might have said, "I will teach you to drive for a $1000"; and you might have said, "That is too much"; but then you allow your friend to teach you to drive. There is probably no contract formed in that situation, but the law does not allow you to accept the services your friend provided without requiring you to pay for them. In that situation the quasi-contractual principles of unjust enrichment or promissory estoppel will likely apply. Unjust enrichment means that you have received something of value by which you would be unjustly enriched if you are not required to pay the value of what you received. Promissory estoppel applies if you induced your friend to give you something based on your promise to pay. Even if a contract was not formed (perhaps because the terms were uncertain), you will be required to pay what you promised if your friend relied on that promise to his/her detriment.
The bottom line is: unless your friend offered to teach you to drive for free out of the goodness of his/her heart, you probably owe your friend something.
This answer is not intended to create an attorney/client relationship. You need specific legal advice from an attorney who can gather all of the facts