I would not worry too much about high school transcripts to be honest. Many top universities will want to see them, but if you have proven yourself at the next level (one to two years of undergrad), you will be fine for admissions. I was very worried about it, so were many of my friends, but we ended up leveraging our poor performance in high school and said that we have revived our academic track record. Use it to your advantage and don’t let it hold you back.