Use of Targets versus Small Goals
Small number games to targets offer a more realistic representation of match conditions than do games attacking small goals (2-4 yards).  This is particularly the case when the practice theme is small number tactics (e.g. 2v2).  How often in your practices when using small goals do the defenders drop in front and stand in front of the small goal while the attackers play "catch" versus exhibiting the principles of attack and defending principles?  Goals are few and repetitions of the tactical coaching points are often fewer.  Try playing 2v2 with a target player at each end of the area (20x20yds) who can move just as a player in a match would move who serves as the target to whom the attackers are trying to penetrate towards as the other two players defend.  Require a combination, e.g. a wall pass, before penetrating to the target player.  If your groups of two are evenly matched, play "scorers keep" where if the penetration is successful those two players get the ball back and attack towards the target at the other end.  In some exercises, a target line is sufficient (e.g. dribble or pass under control over a line).  Match play requires realistic match conditions during practices.  Try targets (players or lines). My guess is that you find as I have that using targets better simulates match conditions.

Shooting on Net
In the end, where a player contacts the ball will determine in what direction a shot will travel.  One way to help keep a player's shot on target and not over the top of the goal is to watch the player who consistently hits the ball high to confirm why they are contacting the ball below its center (therefore causing the ball to sail high).  One coaching tip is to be sure that the player's last longer stride into the ball does not serve as a breaking action to their movement through the ball. Often a player who takes this longer stride slows down as the foot is planted which slows the body's momentum through the ball.  Watch the player's speed into the shot and be sure they are maintaining their speed through the kicking action.

Practice Length
At our NSCAA non-residential courses, numerous youth level coaches ask the question "How long should my team's practice sessions last?"  The NSCAA's staff recommends a coach conduct practice for the length of time equal to the time of their team's matches.  And don't forget to start and, most importantly, end your practices on time. Plan before you arrive and adjust the practice plan as needed. Remember that players are at practice to play so end your youth practices with a small-sided soccer game.