Stop being paranoid.

your daughter has done very well. However. . .
Fact - many kids of today are way out of control, drugs, violence, anti-social behaviour etc.
Fact - many kids today (in the UK at least) are drunken alcoholics at age 14 and have possible renal problems (ref Panorama BBC1 last night)
Fact - many kids also live in isolation and never know how to interact because they prefer the PS2 or the TV in their room.
So, parents try to "encourage" the kids to get good grades by promising stuff - money, a car or whatever. That could be construed as bribery and corruption.
Its well known that the USA survives on bribery and corruption at all levels, the police, the military, the awarding of government contracts etc etc
So, offering kids "incentives" is tantamount to conditioning the kids to learn that to "get on" in life, corruption and bribery is the way to go, especially in the USA.
I'm offering an opinion generally. View it how you like.
Col