1.The advantages are:the communication with( exchange of )native English speakers can improve(increase) their language skills; can know (find out) more about foreign customs and culture.
The disadvantages are not useful for improving scores (performance); with the foreign teachers cultural differences,communication with difficulties,and the high cost of employing foreign teachers.
2.The advantages are:the communication with( exchange of )native English speakers can increase their language skills; can know (find out) more about foreign customs and culture.
The disadvantages is that it's imposible in improving one's level of English ,difficult in culture with foreigners.communicate with foreigners difficultly,also the cost on employing foreigners is high.