Scorekeeper interrupts

[rsl]

Since I'm a newbie and ref mostly Soph/JV, I often have untrained student scorekeepers, and they sometimes (several times last year) blow the horn during a live ball, for example

1) while the shooter has the ball during a free throw
2) While the thrower has the ball at his disposal during a throw in
3) during live play

When the horn blows, In (1) the shooters rhythm is interrupted, and in (2) or (3) we often have half the players stop. Should we always immediately stop play?