Please help a couple of coaches

[Rufus]

We're playing in a youth league that uses NFHS rules (I've ordered my rulebook but it's not yet arrived). We're at our first practice today and I'm going over with the baserunners what a pitcher can and cannot do, more specifically what they should be looking for. Here are my questions:

• Are there any differences in balk rules for NFHS vs. OBR vs. NCAA (In reading prior posts it doesn't appear there are but would appreciate confirmation of that). Specifically then:
• R1, no outs, RHP engaged with the plate and in the set position. For purposes of argument he steps directly to 1st (don't want to get into how high he lifts his leg, whether it goes behind the plate, or discussions about 45 degrees - just steps directly to 1st) without disengaging from the plate and throws the ball to 1st (i.e., doesn't feint). Is that a balk? I don't think it is. My fellow coach said it is because he didn't disengage with his pivot foot backwards off the plate first.

I know this topic has been covered a lot and I appreciate your responses and NFHS rules reference (especially if I'm correct but even more so if I'm not and need to learn the rules better).