In my opinion, parents are the best teacher of all teachers.
.... This is not wrong, but I feel it is good to introduce the topic in your first two lines and then state your opinion.
There's no limitation and boundaries between parents and the children in learning process in terms of time and subjects they give to their children.
I think you can present this better :)
Overall, this is a very good essay.... excellent structure, ideas, presentation .... you surely can go for a very good score :)
Good Luck!