This is my favorite place to stay by the river. Schoolhouse has two camping areas, one in the redwood grove above the highway, and one across the road on the river. Both are nice. Each spot has tent sites, table, and a fire pit. Buy your firewood in town though, because it tends to be expensive and green from the front desk.
The river side has larger sites for group camping. The bathhouse is on the redwoods side, with showers, toilets, & running water.
Schoolhouse park has it's own natural fun to offer, with access to the river and some hiking trails through the redwoods.
Basic fee is $25/night for two people. Each additional person is $5 more.