Students can participate in youth exchange program but there is no such for school teachers. Why?

Because teachers and authorities assume that teachers have already learned enough and their role is to "teach" what they've learned. This is a classical model of thinking which ignores the fact that teachers stop learning once they start teaching.

 Peer-peer learning is one of the most effective learning approaches, so those who know the value of continuous learning will take it into consideration. 

first, i like to inform that the student's exchange happened between schools that follow the same curriculum K and most of the time k between branches of a same school spread in many country - the teacher's exchange happened also between these branches and can be very efficiency because they chose skilled and high quality teachers to exchange new methods of modern learning's styles, so each school can learn new methods used in the other, and that help to develop education by sharing ideas and skills

in other world, the exchange between schools that followed different curriculum is not safe but they can exchanged administration so they can assess the 2 curriculum and to choose what they can add or regulate to develop their curriculum

Maybe because teachers are not young anymore.

I agree with Said Kamha Ph

sorry i have no idea thank you for your question sir 

we should improve our education process 

So many institute offer exchange program for teachers as well. It grooms their staff.