This past year NFHS Rule 6-23-4 was updated allowing attacking players to be in the crease so long as they don't make incidental contact with the goalie or impede the goalkeeper's vision.
The most obvious, yet rare, violation of visual impairment occurs when a skater turns, faces the goalie and takes away his/her sight line to the puck. As has been indicated, this visual impairment results in a stoppage of play, if a goal is scored it is disallowed, and the faceoff takes place at the nearest neutral zone faceoff spot. In addition, officials need to talk with the coach of the offending team. If this behavior continues by this player or others on this team, officials are to assess an unsportsmanlike conduct penalty.
It is more common for skaters to arch around the goal cage and then through the crease and impede a goalkeeper's vision. This may be a distraction, however, it is not allowed when the opposing skater blocks the goalies line of sight to the puck while the skater is in the crease area. When this visual impediment occurs, play is shut down. It is most likely this situation will occur when a shot is being attempted.
Officials are reminded to communicate with goalies as needed. In addition, look for body language with goalies. One easy way to identify visual interference is when a goalie is struggling to see the puck.
NFHS Rule 6-23-4 in its entirety reads as follows: "No attacking player who is in the goal crease (body and/or stick) may make incidental contact with or visually impede the goalkeeper. PENALTY: Stoppage in play, if a goal is scored it shall be disallowed, faceoff at the nearest neutral zone faceoff spot. This rule applies if all of these conditions are met: (a) the attacking team is in possession of the puck, (b) the goalkeeper is in the goal crease, and (c) the puck is not already in the crease. Note: Regardless of the location of the goalkeeper or the puck, if the goalkeeper is physically prevented from defending the goal, apply Rule 6-17-5 or 6-17-6.