Success rates for youth loans dependent on league?

[General]

Harris has been given a loan to conference side Woking.

Benefits of loans is evident, a younger player playing with more experienced players, playing for points and more physicality with greater demands on them.

But what, if there are any, are the standards or statistics for a player who A) gets a certain amount of loan time in and B) at which league?  - and how does that correlate to their success as a professional?

For example what's the most regular level an academy player can get to if they start out in the conference?

If an academy player starts at the championship how often do they go up or find their level in the championship?

What % of academy players that make it to the championship make the grade for a premiership team? Even with Roberts, hyndman and sessegnon - sessegnon is probably the only one who's likely to succeed as things stand in the league.