Here are my comments:
Many past studies shew -> I have never known this phrase before, normally it used in present perfect tense.
Voluntary works are practical and effective educational methods -> Voluntary works can not be methods, methods mean approaches, techniques or manners which help ss gain st better.
Voluntary works are practical and effective educational methods ->It is your topic sentence, so the next supporting sentences should focus on 'practical" & "effective". Whereas, you mentioned other idea relating to "humanity values" later, your paragraph seem not cohenrence.
In general, you have some good ideas. However your ideas are not very clear. I suggest that you should use link words like "on the one hand", "on the other hand", in adition, firstly, secondly, etc... which will help separate the ideas and make your point of views clearer.
Here is my essay which I try to rewrite from yours and utilize your ideas. Tks
Many recent studies have shown that the more an individual engages with his society in a meaningful way, the happier and healthier he becomes. That is not to say, every highschool student should participate in unpaid community tasks without his own interest and will.
On the one hand, I agree that the voluntary work is a practical and humanity-oriented education program. Firstly, the activities in real life provide students with chances of self-assessment, meaning that they would perceive what they are best capable of or interested in. Such cognitions, in turn help students have better decision on future career path after graduation. For instance, a young would not have fluctuation feeling to apply to Medical University after his summer volunteering program in helping patients at hospital as if he felt interested in the job here. Secondly, most community programs promote humanity values among highschool students as they are associated with the less fortunes. When students take part in such programs, they have opportunity to work with vunerable groups in society and could learn that life is diverse and mankind would be better off helping each other. From this, they have more morality lessons than what they learnt from textbooks.
On the other hand, I argue in favour that making this activity a compulsory program in curricula would lose the initial meaning of the service and entails unforeseen consequences. When a voluntary work is conducted in reluctant manner, it could be becomes a burden for both sides of providers and receipents of such service. For example, most unpaid services are now provided to support disadvantaged groups in community, so the people who receive helps wouldl feel hurt if they know the highschool students are not willing to do that. In addition, the students can also face difficulties in choosing the service which match with their ability and interest. In case they are forced to do what they are not keen on, they can not perform their ability at best and even have negative attitude toward the voluntary services. Therefore, the educational purposes of the volunteering program can not be achieved as it is expected at beginning.
Overall, I slightly disagree that highschool children should be obliged to join unpaid community deeds. The alternative way to encourage students to do social works is to make it an optional subject in the curriculum and increase children’s awareness about the program so that they could voluntarily register to make their contribution.