The high capacity of the skill of acceleration/speed is considered as an integral part of the modern soccer player. Over 80% of the sprints in a game are until 10 meters. For the most reliable speed measurement method use photocells.
Do not miss to execute the speedtest of 30 meters with another gate at 10 meters (many place them and at 5 meters) as well, with a lot sport scientists consider as more important the good times at these meters.
If you refer to the literature you will find many variations as to what time is considered ''good'' (the diversity of findings obviously ought to differences in the level of the athletes and the execution of sprint surface or the distance of the foot from the starting gate).
I would recommend you to create your own norms in your team by placing 10% of the best times in "good" performance. If again definitely you want a comparison, consider the times less than 1,71 sec at 10 meters on the grass surface, as a "good" time.