[squid-users] Only 23% of traf is cached. Config problem?

These are my Squid stats. I have about 23% of cache hits.
We have 300 users. This is a school environment where most students
access the same site at the same time for their classroom activity.
Is there anything I should add or change to make the caching better,
or is 23% to be expected?

Proxy statistics
Total amount: requests 263,840
Total Bandwidth: Byte 2634M
Proxy efficiency (HIT [kB/sec] / DIRECT [kB/sec]): factor 5.72
Average speed increase: % 16.58
TCP response time of 100%% requests: msec 5048

Cache statistics
Total amount cached: requests 61936
Request hit rate: % 23.47
Bandwidth savings: Byte 454M
Bandwidth savings in Percent (Byte hit rate): % 17.24
Average cached object size: Byte 7686
Average direct object size: Byte 11319
Average object size: Byte 10466

Squid box is 2.4 GHz P4, 1GB memory, 40 GB IDE disk.
Squid version 3.1.3 on Debian.

Config file:
acl manager proto cache_object
acl localhost src 127.0.0.1/32
acl to_localhost dst 127.0.0.0/8
acl localnet src 176.16.0.0/21 #176.16.0.-176.16.3.254 range
acl localnet2 src 192.168.11.0/24 #192.168.11.0-254 range
acl localnet3 src 192.168.200.0/24 #192.168.200.0-254 range
acl SSL_ports port 443
acl Safe_ports port 80 # http
acl Safe_ports port 21 # ftp
acl Safe_ports port 443 # https
acl Safe_ports port 70 # gopher
acl Safe_ports port 210 # wais
acl Safe_ports port 1025-65535 # unregistered ports
acl Safe_ports port 280 # http-mgmt
acl Safe_ports port 488 # gss-http
acl Safe_ports port 591 # filemaker
acl Safe_ports port 777 # multiling http
acl CONNECT method CONNECT
http_access allow manager localhost
http_access deny manager
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports
http_access allow localhost
http_access allow localnet
http_access allow localnet2
http_access allow localnet3
http_access allow all #not restricted because its behind the firewall
and serving local LAN only. I'm just trying to get this working for
now...
icp_access allow all
htcp_access allow all
http_port 3128 transparent # ok, transparent proxy, no NATing. Not
sure what WPAD/PAC is...
hierarchy_stoplist cgi-bin ?
access_log /var/log/squid3/access.log squid
refresh_pattern ^ftp: 1440 20% 10080
refresh_pattern ^gopher: 1440 0% 1440
refresh_pattern (cgi-bin|\?) 0 0% 0
refresh_pattern . 0 40% 40320
icp_port 3130
coredump_dir /var/spool/squid3
refresh_pattern -i \.index.(html|htm)$ 0 40% 10080
refresh_pattern -i \.(html|htm|css|js)$ 1440 40% 40320
cache_mgr help_at_mydomain.org
cache_dir ufs /var/spool/squid3 7000 16 256
visible_hostname gw.mydomain.org
Received on Wed Sep 29 2010 - 20:39:33 MDT