pintu,
it's a 50-50 thing for students as I see. the custom in KTM  may or mayn't object depending upon their mood, weather in KTM (since it has some impact on mood),  ghadi--palaa or Time (since it has some positive/negative astrological effects on mood of the custom officers), flow, traffic and all...

if they catch you carrying 3 laptops, they would probably not spare you credits for being a "student". More so now as the new governement have made things stricter for people carrying more stuffs (electronics especially)

in suammary, i would say: take just one or else carry them all but at your own risk (of having to pay the tax for all but one)