Switching from VWP to a US F-1 visa

Yes, this is allowed.

On the first entry to the US:

After clearing the automated passport kiosk (no need to fill out the blue customs form you get on the plane), present the receipt and the passport open at the main ID page
Have in hand, but don't present upfront, all available documentation proving you will not start studying in the US immediately, and that during this stay, you will only be a visitor.
Proceed as normal and you will enter in WT Status
When exiting to Mexico, your exit will be electronically recorded, so it will be clear that you left the country.

When re-entering the US from Mexico:

Fill out the blue customs form you get on the plane, and do not use an automated kiosk.
Present the blue form, the I-20 and the passport open at the visa page.
Proceed as normal and you will enter in F-1 Status.

Crazydre 74291

Source: stackoverflow.com