Improvements in a stackable construction panel system are disclosed. The system includes stackable wall forms for receiving a flowable material, each form having a pair of foam panels tied together in a spaced and parallel relationship by connectors. In a first improvement, the connectors have head pieces with transversal terminal surfaces facilitating the stacking and handling of the wall forms on construction sites. In a second improvement, an end panel assembly is provided for mounting an end panel used as a wall stud for the construction of a window or door frame. The end panel assembly has first and second engaging members, each removably engageable with side end portions of the pair of foam panels. The end panel itself is mountable therebetween. In accordance with a third improvement, a corner connector is provided for reinforcing corner wall forms.