Oh boy! What to say? First the bad.
This was soooo grim. Fourty screaming children stuck on the wall. All of the assault team about to be cut down in a dank stone building. (I'm sure you're a nice person, but really...)
Now the good.
You write really well. No typos, good grammar, and dialog that reads easy and natural. The sentence structure was varied and nothing read in a sing-song manor.
Albus selling out Harry in such a way and the castle scene were unique.
Powerful stuff!