Review Of DB Design - Normalized, Contraints, Foreign Keys, Etc.

First of all, this is my initial thread here on dbforums. I come from the land of Broadband Reports and would like to say, Hello fellow DB enthusiasts. :)

I'm not a novice to relational databases (Access MDBs), but new to implementing a db via SQL SERVER (2000 in this case) and using Access Data Projects.

My partial db schema is as follows:

participants
---DID (pk) char(1)
---LID (fk - schools) char(4)
---studentLast varchar(50)
---studentFirst varchar(25)

Sample Data would be
010191M001 | 5671 | SPARKS | JONATHAN
030495F283 | 5671 | DYLAN | CYNTHIA
=====================================

enrollhist (insert/update trigger for enrollactive)
---EID (pk - autonumber) bigint(8)
---EMID (fk - enrollmode) int(4)
---DID (fk - participants) char(10)
---LID (fk - schools) char(4)
---enrollactive bit(1)

Sample Data would be
38173 | 4 | 030495F283 | 9003 | 0
38266 | 3 | 010191M001 | 5671 | 0
39022 | 6 | 030495F283 | 9003 | 0
39036 | 5 | 030495F283 | 9003 | 0
39044 | 4 | 030495F283 | 5671 | 1
39117 | 4 | 010191M001 | 5671 | 1
=====================================

enrollmode
---EMID (pk) int(4)
---mode varchar(25)

Sample Data would be
1 | RECEIVED
2 | WAITING
3 | PENDING
4 | ENROLLED
5 | DROPPED
6 | TRANSFERRED
10 | ORPHANED
11 | DENIED
=====================================

schools
---LID (pk) varchar(4)
---CTID (fk - caltracks) char(1)
---AID (fk - agencies) char(1)
---SDID (fk - schooldist) char(1)
---COID (fk - countydist) char(1)
---sitename varchar(25)
---sitetitle varchar(75)

Sample Data would be
5671 | 3 | 2 | 1 | 4 | ASCOT | ASCOT AVENUE
9003 | 2 | 1 | 4 | 1 | ROWAN | ROWAN AVENUE
2865 | 1 | 3 | 2 | 3 | BRIGHT | BIRDELEE BRIGHT
=====================================

caltracks
---CTID (pk) char(1)
---legend char(4)
---trktitle varchar(15)
---trkcnt int(4)

Sample Data would be
1 | 9030 | 90/30 | 4
2 | CON6 | CONCEPT-6 | 3
3 | SNGL | SINGLE TRACK | 1
=====================================

agencies
---AID (pk) char(1)
---legend varchar(4)
---agencytitle varvhar(50)

Sample Data would be
1 | CRYS | CRYSTAL STAIRS
2 | MAOF | MEXICAN AMERICAN FOUNDATION
3 | PATH | PATHWAYS
4 | CCRC | CHILD CARE RESOURCE CENTER
5 | CHSC | CHILDREN'S HOME SOCIETY OF CALIFORNIA
==========================================

THE REMAINING "FKs" FROM SCHOOL ARE SIMILAR, as is other tables and their relationships. The design of the foreign keys were made using sql and the keyword "REFERENCES" and "FOREIGN KEY."

My questions are: :confused:
(1) Is the use of FK as a Constraint any different than using an INDEX and how?
(2) Should I Alter the Tables to include CASCADING Up/Down?
(3) Are the use of CHARs Ok for the Keys?
(4) Have I over/under-normalized any of the relationships?