It sounds like a great idea. I've enclosed a link to another colonial herb garden, might give you some ideas.

It would be quite interesting to research exactly how your herbs were used. Dye plants were very important, and they still work today. Weld (Reseda luteola), Madder (Rubia tinctorum), Woad (Isatis tinctoria) -- don't know when that was replaced with Indigo, which gives a much better blue.

http://tntn.essortment.com/growingdyeplan_rgia.htm

Some historical medicinal uses are still valid today, others have been discredited, and some are downright dangerous or poisonous. Some good research possiblities. You might also track the subtle shift in the meanings of the word "herb" since colonial times.

Here is a link that might be useful: Colonial Garden, Maine

Another use of herbs was more decorative. Handmade brooms had aromatic herbs bent in with the broom bristles, for example.

Here is a link that might be useful: Decorative wreaths with herbs

If you look into your neighborhood nurseries and find one that will aid you in perhaps free plants by way of cuting that could give the kids an easier way to propagate than doing seeds. This could be the perfect time to do that as most centers are winding down for the season. They may also have some other connections for sources such as historical places you could drawl from for your project. I've tried doing seeds with children in the classrooms and found most where very leggy and stressed when it was time to plant outside. Although direct sowing would be best for your raised beds. If your going to start seeds check in the cafateria for extra trays so they wont make a mess when they need to be watered. You might want to tie your garden in with the classic victory garden theme. The gardens were not just all about veggies and that has a history all to it's self. Dried flowers could be used for other projects. This way more teachers could get involved with the lesson plan. You may also get some free cell packs for the garden ceneter along with other goodies. Alot of that stuff gets tossed. It hard to say no to a bunch of children saying please. Good Luck.

Here's a link that may give you some more direction.

Here is a link that might be useful: http://www.gardendigest.com/timegl.htm#Start

Some printed resources that you might find useful are "Early American Gardens" by Ann Leighton, ISBN 0-87023-530-3, which covers the 17th century. She also published two other books, on the 18th century (out of print) and 19th century. "The Herb Companion" magazine carries lots of articles on old herbs. A back issue vol.8 #3 (Feb/Mar 1996) had an article on America's Oldest Physic Garden, at Winston-Salem, NC, circa 1761. Try their website.