The ornamental design for an educational wallchart, as shown and described.
FIG. 1 is a perspective view of an educational wall chart showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines immediately adjacent to the claim and define an unshaded region depict the bounds of the claimed design, while all other broken lines are directed to environment. The broken lines form no part of the claimed design.