Read the following article by Alexander Rose (Author of the "American Rifle") it would appear that compared to their contemporaries they were very good. Very Good. Try this link.
http://www.americanrifleman.org/ArticlePage.aspx?id=2455&cid=5&utm_source=newsletter&utm_medium=email&utm_content=1775-text&utm_campaign=TaurusRossi
Sven
Reposted from the Minnesota Board
The truth is in the casualty list from April 19th, 1775.
Gage's 1800 men had suffered 73 killed, 174 wounded and 26 missing, just over 15% casualties. About 3500 militia were actually engaged and suffered 49 dead, 39 wounded, and 4 missing for a rate of about 2%.
Surely, the logistics of it had an effect as well, but if the Militia were truly all poor shots with little or no practice - the Regulars would have surely faired better.