on the account of
-> on the grounds that
not reliable to others
-> not reliant on others. Reliable means trustworthy.
This is because they believe the sense of competition is do it alone in teaching children
-> What do you mean by "do it alone in teaching children"? I'm quite confused.
experts explained
,
they also believed
I think you should use present tense rather than past tense in these cases.
In concluded
-> In conclusion/To conclude
competition and cooperation both
-> both competition and cooperation