I went to Catholic school until I was 8 and then went to public schools but I think I'm older than you. Also, the schools were in upstate New York until I was a teenager and upstate was and still is fairly conservative.
Teacher bias in the 50's and 60's didn't seem as blatant to me as it seems now.
David Horowitz is working with members of Congress to introduce legislation that would require a more fair and balanced curriculum in colleges; it looks like he should take a look at the lower grades as well.
His personal turf is academia, but I believe it all starts first at home, then in primary and secondary school. I admit though that college professors are openly leftist and definitely anti-Republican. However, students routinely choose their college. This isn't true for primary and secondary school, since most parents aren't about to buy one school for the price of two.
The only answer is to abolish public schools. That's the goal we should strive for. It would likely reduce leftist indoctrination and would DEFINITELY improve the quality of education.