iPad Mini 4 poweron

My iPad mini 4 does not power on anymore. I received the iPad mini 4 from Donors Choose. I am a teacher and at the end of each day I lock up the iPad. When I come in the morning I take it out of my closet and use it. Only I use it. My students use the school's ipads.

This time I came in the classroom and tries to power it on and it didn't. I tried multiple outlets, different usb cords and adapters, and even tried charging it on my laptop. Nothing has powered it on. I feel it get hot when I was charging it for about an hour.

I don't know what the problem is? Please help!