Kids from different economic backgrounds behave ___56._____(different) in classrooms. For example, working-class kids are ___57._____likely to ask for help from teachers than their middle-class counterparts. And   when/if they do ask for help, they’re less aggressive about it.

That’s according to a study that followed students from the third grade through the fifth, ___59._____(publish) in the journal American Sociological Review. Part of the difference in how kids act ___60.____(come) from the guidance they’ve gotten at home. As ___61.____ rule, working class parents coach their kids to work out problems on their own. And if the kids did ask for help, it was in subtle ways—like sitting quietly____62.____a hand raised. Middle class kids? Their parents urged _________( they) to be proactive, even to interrupt their teachers for help.

 The result is that teachers were more likely to attend to the assistance-seekers and louder class-participators,_____64.____ left working class kids behind and magnified inequalities.

请问这里是用 when 比较好，还是if 比较好。