Manifesting is a baseless craze, better known as 'wishful thinking' and is on par with praying for things to turn out well.
"manifesting feels like a way to accomplish something we have control over in a time when we’re mostly powerless to effect any real change. There is also a lower barrier to entry than almost any other activity: All you need are your dreams, and to think about how nice it would be if they all came true."
I hope you get into your dream school and get good grades but you may need to take your likely failure as a learning point.
It sounds like the places will go those with better planning skills, who applied before the deadline, and who devote themselves to their studies.
What practical, rather tham spiritual, steps can you take to get into that school, or another? Can you defer or take a gap year, for example?