It's a bit more complicated than just finding a flying school or suitable program for your son...
Firstly, he'd have to finish the equivalent of high school - that means Grade 12 in the Canadian system. You could consult the Canadian Embassy or Consulate in your area for more information.
He'd also have to gain the ability to reside in Canada in order to attend whatever course you may feel is right for him. Again, see the helpful staff at the nearest Canadian Embassy or Consulate.
I'm familiar with two schools in Western Canada:
www.mtroyal.ca
www.selkirk.ca
You may also wish to ask the same question you've asked on this forum in New Zealand or Australia, both of which are slightly closer to Nepal... they have excellent schools there as well. So does the UK (more expensive due to currency exchange) and consider South Africa and the USA as well.
Good luck.
M-rat