Carb,
The U.S. Embassy Website is quite clear about the Visa Waiver Program:
Details about the Visa Waiver Program
Important reminder: Visa-free travel does not include those who plan to study, work or remain more than 90 days. Such travelers need visas. If a U.S. immigration officer believes that a visa-free traveler is going to study, work or stay longer than 90 days, the officer will refuse to admit the traveler.
The U.S. Government has been very clear. After terrorist used aircraft to attack the U.S.A. on Sept. 11th, they are not going to allow it to happen again. The way they are insuring this is by having anyone planning on flight training in the U.S.A. have a background check prior to training. To guarantee a background check they requiring everyone planning on training to be on an F-1, M-1 or J-1 Visa.
If you want to ignore the law and take your chances entering the country illegally and under false pretenses, there is nothing we can say here to stop you. But, to try to encourage others to do the same is irresponsible.
Richard