I think it would be difficult to do with a preshooler who is "average" but probably more kids could be taught to read earlier than they are in school if the parents put more effort into it. I tutored reading last year (grades 1-3) and the kids I worked with were probably average IQ, (and just below target for reading fluency) but clearly didn't learn how to read the same way my own two did. They had to read the same passages over and over and over before they became fluent, and every time they made an error I corrected it and made them read the sentence over again. At times I felt like pulling out my hair. These kids who were 8-9 years old were struggling more than my own kids did at age 4. So if someone had tried to "hothouse" them in preschool, they would have given up after about 1 day--it would have been way too frustrating and impossible for the kids. I do think a kid needs to be above average IQ to learn reading in preschool but probably not "gifted". My SIL is a teacher and thinks her own child is brilliant because he started to read before kindergarten. She spent tons of time talking about letters, letter sounds, etc. I would guess he's above average but not gifted (I refuse to use the term hothouse in her case since it sounds so negative--I don't think there's anything wrong with what she was doing and save the term for clearly pushy parents who are trying way too hard with a kid who isn't ready).