So, here goes.

Spelling and Grammar:

I walked into the office and breathe in a huge breath.
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'Breathe' should be 'breathed,' and I believe 'breath' should be 'breathe.'

Ms Robinson, my Residential Supervisor looks at me.
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You need a comma after 'Supervisor.'

“Jessica when you have a minuet, Ms Mac and I would like to speak to you”
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You need a comma after 'Jessica' and 'you.'

“Jessica it has come to my attention that someone outside of Glennwood found your blog “No Day But Today and has read it”.
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Should be:
“Jessica, it has come to my attention that someone outside of Glennwood found your blog, 'No Day But Today,' and read it."

I dialed my home phone number “Mom I did something bad” I choke out.
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You need a period after 'number' and a comma after 'bad' and 'Mom.'

Always start a new paragraph for dialog. Always.

That's a light brushing through. I would suggest working on your proofreading skills (they take forever to develop but the pay off is amazing)and get a beta reader in the meantime by looking on livejournal, among your friends, or on the forums.

Style:

I looked at her, total shock washing over my normally good natured features.
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As it's in the first person, put in details that she would notice. Instead of physical description of her face (which she can't see) say something about the actual feelings involved.

I walked into the office and breathe in a huge breath.
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I wasn't sure if this was intentional to give her a personality and mindset, but if it is, you need to carry this style through the entire piece.

The narration lacks emotion and personality. Who is Jessica as a person? What are her thoughts during this experience? Set up a setting and mood. It will help a lot with the plot.

Practical:

Even in a blog concerning drug use, cutting, or even hallucinations, I doubt that many people would be involved. Probably the vice principle would work behind the scenes and the school councilor would be the one she actually meets with.

What you did well:

This leaves a lot in shadows, which is good. I have to wonder what her blog actually said. The switching of scenes is nice, it builds suspension without trying to hard.

Respectfully yours,
Feather La