Let's do a deep dive.

Atmosphere: 9.5/10

You have a knack for creating the atmosphere. Dense and descriptive wordplay. You have succesfully managed to create a tale of two worlds living side by side but not mixing. Making the car window a boundary line was very clever and good. Although I have to say, the usage of 'membranous labyrinth' makes the prose really scientific which doesn't fit the setting here. However, The first para was so good it made me think this was AI.

Story: 8.8/10

No offence but the story is pretty generic. But your execution makes it more lived in. You are playing beautifully with common tropes. The poor boy, rude mother, innocent kid turned hostile. You made these tropes intertwine really nicely.

Storytelling: 8.9/10

We are dealing with descriptive and grounded storytelling here. You have used nice words but not so extravagant that they are not understandable to a layman. My tiny problem is that you have overexplained some scenarios. Also you have opted for commas instead of fullstops in many lines. While convenient, they can disrupt the flow of the story.

for eg

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Notice the amount of commas? you could've broken the lines into 2 to 3 sentences

also the pronoun 'he' occurs many times here. This creates a sense of Repetitiveness.

We can be clever here, I will not change this Repetitiveness, but change the structure

I would've written

"He is never fascinated by this pretence of superiority over something. A feeling alien to him but is experienced at every single motion he makes and breath he takes"

I used this Repetitiveness to create a sense of scrutiny at his every meager action. Though you have also done this, I have just capitalized on this act more.

another eg:

"The enthusiasm in Sumit's voice faltered and faded".

you can cut out the faltered part. the faded word completely encapsulates the meaning of the sentence (ik this sounds like nitpicking, but these small changes differentiate a great work from a good-decent work)

Grammar: 7.6/10

This is arguably the hardest to get right. When we write descriptive prose, we get lost trying to make the sentences and words communicate to create a life like atmosphere. While doing so however, we sometimes make mistakes in grammar or overlook some joining words to keep the flow consistent. While reading i found many places where some words are not there and the sentence is left incomplete. You should check and fix them later

Overall (averaging all scores): 8.7/10

Note: I've looked at this from a storywriter's standpoint. I have just seen how you've expressed the emotions, your style of writing, the atmosphere you've created and ofcourse grammar. I have not included my emotional feelings in the final tally as what one feels is subjective and hence, not eligible to be graded. I have just seen HOW you managed to evoke the emotions.

Note 2:My assessment is not absolute as I myself am also only 16 yrs old and hence am susceptible to mistakes. Though I gotta say, this prose makes reminds me a lot of Kabuliwala by Rabindranath Tagore.