trying to buy a present for a 5 ft 13 year old boy for dirt jumping and general street thrashing.
race bike sizes i understand but it seems more limited the other side of bmx
any help would be great thanks.

http://www.danscomp.com/101122.php

DK Ordinate - complete on sale at Dan's $224.99

Hi-Tensile steel frame with a chromoly down tube, DK fork with chromoly steerer tube, DK chromoly 7.3" bars, DK grips, DK frontload stem, 1-1/8" standard headset, detangler, Tektro brake and lever, 3-pc tubular chromoly cranks with sealed Mid BB, 33T chainwheel, 3/8" front hub, 14mm rear cassette hub with 12T cog, 36H alloy rims, DK Street seat, alloy platform pedals and DK pegs. 19.5" Toptube. (28.1 lbs)

I don't know if you're on a budget, but if you are, this would work. 19.5" top tube is shorter than most other street bikes. 7.3" bars are also lower than the typical 8"s. Should fit him pretty well.