My daughter has this. We eventually homeschooled her. The sitting to standing to get up from one class to another made her so dizzy.

She still has moments of dizzyness...but she has learned how to get up slower, which helps with it. We also have to have her get regular blood work, anything that might affect her heart needs to be caught right away.

Her quality of life got better after we took her out of school and she learned how to get up slower. It can still be an issue for her at certain times...it stinks and I am sorry to hear you have this.

Good luck