More Music Lessons in Schools

There should absolutely not be any more music lessons in school.

In fact, the upper-elementary school kids will (should) start to learn English from this April on/onward instead of increasing music lessons. "will" doesn't match with "should" above. Either change it here or change "should" above.

First of all, are facing a knowledge-based society now.

It requires that children to understand how to deal with information in society.This would fit better as relative clause modifying "society" above:'... a knowledge-based society now which requires that children understand...'

Therefore, teachers must (have to, implies their bosses/the government are saying to do this; must implies you think they should) teach how they should think and do on their own through the humanities and the science more than arts.

Secondly, there is a huge gap/world of difference between the music taught in school and the music for entertainment.

Pop is the mainstream of the music market.

In addition to this, school teachers don't introduce all the genres from classic to rock; it is impossible to do so with the time allotted. (or, —it's simply impossible with the time their allotted. (— is called m-dash in the insert symbols section))

Finally, school generally don't have a budget allowing kids to have their own instrumentals.

Consequently, unless children belong to music clubs, they seldom have chance to actually play their instruments.

It is not at all interesting just to sing or play handy ones for many years.Not quite understanding you:Perhaps, 'It's no fun just to sing or play old hand-me-down instruments.'

In conclusion, it can be said, then, that music lessons should (again, keep using the modals. Because this is meant to be your opinion 'should' 'could' 'would' are you best options) not play a main role in school education.The transition is kind of stilted. Try 'In conclusion, music lessons simply should not...'

For that reason, There should not be more music lessons in schools.Or more strong, 'Music lessons should be disbanded/removed/taken out from schools.'

There should absolutely be no more music lessons in school.

In fact, the upper-elementary school kids student will start to learn English from this April instead of increasing music lessons.

First of all, we have faced the live in a knowledge-based society now.

Finally, school does not schools generally do not have plenty of a school budget for kids to have their own instrumentals.

In conclusion, it can be said, then, that music lessons do not play a main important role in school education.