With all due respect to those who labor in cinder block halls, high school can reasonably be characterized as mostly unfortunate. For starters there are those awful prom dress choices, and then there is that seemingly universal and senseless compulsion to forgo jackets and hats in sub-zero weather. But there is also the impression left by your well-meaning English teachers that longer is better. It isn’t.
Don’t try to fit a whole paragraph or even an entire paper in one sentence. Here is an example:
When the serpent shed its skin, it is as if it had been in some way born again, and is somehow associated with the tree and has apparently enjoyed its fruits since it can slough its skin and live again.
Slow down. Present your points in clear and manageable units, preferably units known as simple sentences:
The serpent shedding its skin suggests rebirth. Symbolically, it may be associated with trees that similarly shed their leaves. The serpent of the garden myth probably ate the fruits of the tree of life. Thus both the tree and the serpent seem to die and yet live again.
We are taught the structure of English in stages of increasing complexity. This leaves us with the notion that complexity is better. This simply is not the case. Clarity is the key to good writing. As a general rule, clarity is proportional to simplicity.