As for playing high school ball, it was probably not until around 13 that we felt comfortable. The high school he is zoned for is quite large and tons of kids playing baseball. When you started to look at the raw numbers it was daunting. Son drifted a little bit at 11/12 and it seems like the group of kids in his class that would end up playing was already set and we were on the outside. A year or two and a few more inches helped turn the tables. At 10 year old I probably put the probability at around 25%.
As for college, it was two fold. Part of the process was really understanding the different levels of college ball. I remember someone on this board saying that there is a home for anyone wanting to play at the next level (assuming you can walk and chew gum at the same time). Son just kept getting better and at around 14 I figured he could play at the next level somewhere. As for what level he can play at, the verdict is still out. As he is rather young for his class, I fear that his decision will have to be made before he fully develops. If only we had held him back in preschool....who knows.