Youth fantasy, read in 80s/early 90s, boy who learns magic activated by "door" in his mind. Mentor talks about EQ (vice IQ). Boy saves child from being hit by car with magic. Boy opens up "door" in his father's mind

Details that I remember:

Magic potential was activated by someone "opening a door" in his mind

Mentor talked about his "EQ" (similar to IQ)

At one point boy saves a child from being hit by a car by knocking him down magically (mentor tells him to leave because he's grinning at kid who nearly got hit)

Boy ends up opening the mental door for his father