From the Budget Allocation page "Help" section;
Advance Scouting Department - The advance scouts are responsible for projecting the ratings of all signed players within the franchise and on other franchises. The higher the budget, the more accurate your projected ratings will be for all players who have not yet reached the peak of their career. After a player reaches his peak, projected and current ratings are the same.
ADV Scouting has
zero impact on High School (or College or International) Scouting.