My fist choice route is via Spruce the direct way. Spruce is popular with cyclists of all types, has water at the top, and takes you to within 2 blocks of the northern end of Grizzly. Wide lane provides room for bikes, and drivers are used to seeing bikes.
via Spruce 3.75 miles, +765 feet
via Spruce the long way 4.1 miles, +765 feet
via Arlington Boulevard
This route stair steps uphill, stretching out the climb compared to Spruce. Some tight sections but fairly bike friendly. Short steep climb connects Arlington to Highland. If it's outside of school hours you can continue on Arlington uphill and take Highland right through the Kensington School to cut out the very steep section on Kensington Park Road.
My most direct route. Some steep ramps with recovery sections make good power training. Continue right on Grizzly to the steam trains for a full 1/2 hour of climbing 3.4 miles, +770 feet
Another steep route up South- and Northampton to Spruce.